Validation doesn't warn about duplicated ids and Web/Desktop version handle the manifest differently

Expected behavior

I would expect an error when validating my add-in manifest and it contains multiple elements with the same id.
I would also expect the same behaviour on Mac Desktop and on the browser, however it is not the case.

Current behavior

Duplicated Id are not warned and depending on the platform you get different results. For example, I copy/paste the the Group and Control provided in powerpoint example created and put them on the Office TabInsert. Only the the first (of two) Group and Control is shown on the web, but not the second one. On the desktop version of Mac none are shown. The manifest is valid according to the office-addin-manifest validate manifest.xml

Steps to Reproduce

1. Create a new React powerpoint taskpane add-in using the yo office generator
2. Copy the CommandsGroup element into a new tab: TabInsert
3. Run npm start and you will see that none of the groups is shown
4. Upload the same manifest into the browser version and you will see the first group (TabHome), but not the second one.

Here is my manifest.xml

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<OfficeApp xmlns="http://schemas.microsoft.com/office/appforoffice/1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:bt="http://schemas.microsoft.com/office/officeappbasictypes/1.0" xmlns:ov="http://schemas.microsoft.com/office/taskpaneappversionoverrides" xsi:type="TaskPaneApp">
  <Id>a824e282-73bb-4f9a-8f23-96756fe97090</Id>
  <Version>1.0.0.0</Version>
  <ProviderName>Contoso</ProviderName>
  <DefaultLocale>en-US</DefaultLocale>
  <DisplayName DefaultValue="My Office Add-in"/>
  <Description DefaultValue="A template to get started."/>
  <IconUrl DefaultValue="https://localhost:3000/assets/icon-32.png"/>
  <HighResolutionIconUrl DefaultValue="https://localhost:3000/assets/icon-64.png"/>
  <SupportUrl DefaultValue="https://www.contoso.com/help"/>
  <AppDomains>
    <AppDomain>https://www.contoso.com</AppDomain>
  </AppDomains>
  <Hosts>
    <Host Name="Presentation"/>
  </Hosts>
  <DefaultSettings>
    <SourceLocation DefaultValue="https://localhost:3000/taskpane.html"/>
  </DefaultSettings>
  <Permissions>ReadWriteDocument</Permissions>
  <VersionOverrides xmlns="http://schemas.microsoft.com/office/taskpaneappversionoverrides" xsi:type="VersionOverridesV1_0">
    <Hosts>
      <Host xsi:type="Presentation">
        <DesktopFormFactor>
          <GetStarted>
            <Title resid="GetStarted.Title"/>
            <Description resid="GetStarted.Description"/>
            <LearnMoreUrl resid="GetStarted.LearnMoreUrl"/>
          </GetStarted>
          <FunctionFile resid="Commands.Url"/>
          <ExtensionPoint xsi:type="PrimaryCommandSurface">
            <OfficeTab id="TabHome">
              <Group id="CommandsGroup">
                <Label resid="CommandsGroup.Label"/>
                <Icon>
                  <bt:Image size="16" resid="Icon.16x16"/>
                  <bt:Image size="32" resid="Icon.32x32"/>
                  <bt:Image size="80" resid="Icon.80x80"/>
                </Icon>
                <Control xsi:type="Button" id="TaskpaneButton">
                  <Label resid="TaskpaneButton.Label"/>
                  <Supertip>
                    <Title resid="TaskpaneButton.Label"/>
                    <Description resid="TaskpaneButton.Tooltip"/>
                  </Supertip>
                  <Icon>
                    <bt:Image size="16" resid="Icon.16x16"/>
                    <bt:Image size="32" resid="Icon.32x32"/>
                    <bt:Image size="80" resid="Icon.80x80"/>
                  </Icon>
                  <Action xsi:type="ShowTaskpane">
                    <TaskpaneId>ButtonId1</TaskpaneId>
                    <SourceLocation resid="Taskpane.Url"/>
                  </Action>
                </Control>
              </Group>
            </OfficeTab>
             <OfficeTab id="TabInsert">
              <Group id="CommandsGroup">
                <Label resid="CommandsGroup.Label"/>
                <Icon>
                  <bt:Image size="16" resid="Icon.16x16"/>
                  <bt:Image size="32" resid="Icon.32x32"/>
                  <bt:Image size="80" resid="Icon.80x80"/>
                </Icon>
                <Control xsi:type="Button" id="TaskpaneButton">
                  <Label resid="TaskpaneButton.Label"/>
                  <Supertip>
                    <Title resid="TaskpaneButton.Label"/>
                    <Description resid="TaskpaneButton.Tooltip"/>
                  </Supertip>
                  <Icon>
                    <bt:Image size="16" resid="Icon.16x16"/>
                    <bt:Image size="32" resid="Icon.32x32"/>
                    <bt:Image size="80" resid="Icon.80x80"/>
                  </Icon>
                  <Action xsi:type="ShowTaskpane">
                    <TaskpaneId>ButtonId1</TaskpaneId>
                    <SourceLocation resid="Taskpane.Url"/>
                  </Action>
                </Control>
              </Group>
            </OfficeTab>
          </ExtensionPoint>
        </DesktopFormFactor>
      </Host>
    </Hosts>
    <Resources>
      <bt:Images>
        <bt:Image id="Icon.16x16" DefaultValue="https://localhost:3000/assets/icon-16.png"/>
        <bt:Image id="Icon.32x32" DefaultValue="https://localhost:3000/assets/icon-32.png"/>
        <bt:Image id="Icon.80x80" DefaultValue="https://localhost:3000/assets/icon-80.png"/>
      </bt:Images>
      <bt:Urls>
        <bt:Url id="GetStarted.LearnMoreUrl" DefaultValue="https://go.microsoft.com/fwlink/?LinkId=276812"/>
        <bt:Url id="Commands.Url" DefaultValue="https://localhost:3000/commands.html"/>
        <bt:Url id="Taskpane.Url" DefaultValue="https://localhost:3000/taskpane.html"/>
      </bt:Urls>
      <bt:ShortStrings>
        <bt:String id="GetStarted.Title" DefaultValue="Get started with your sample add-in!"/>
        <bt:String id="CommandsGroup.Label" DefaultValue="Commands Group"/>
        <bt:String id="TaskpaneButton.Label" DefaultValue="Show Task Pane"/>
      </bt:ShortStrings>
      <bt:LongStrings>
        <bt:String id="GetStarted.Description" DefaultValue="Your sample add-in loaded successfully. Go to the HOME tab and click the 'Show Task Pane' button to get started."/>
        <bt:String id="TaskpaneButton.Tooltip" DefaultValue="Click to Show a Taskpane"/>
      </bt:LongStrings>
    </Resources>
  </VersionOverrides>
</OfficeApp>

Context

• Operating System: MacOS & Browser (Edge, Chrome, Safari)
• Node version: v22.13.0
• Office version: Desktop 16.95.4 (25040241), Browser: 16.0.18731.40500

Failure Logs

None

Start with the office-addin-manifest validate manifest.xml entry point and use the manifest in the issue to reproduce the duplicate Group and Control IDs. Trace the validation behavior and existing checks; done means duplicate IDs are reported and the result can be verified against the documented web and Mac behavior.