Real Time List Auto Updating (Co-auth) not working with Form Customizers

Target SharePoint environment

SharePoint Online

What SharePoint development model, framework, SDK or API is this about?

💥 SharePoint Framework

Developer environment

Windows

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

• browser version - Edge Version 135.0.3179.54 (Official build) (64-bit)
• SPFx version - @microsoft/generator-sharepoint@1.20.0
• Node.js version: v18.20.6
• Spartan build odsp-web-prod_2025-03-28.009splistwebpack/

Describe the bug / error

When utilizing a Form Customizer in the new Spartan SharePoint List UI (such as SPFx, InfoPath, Power App, PowerShell), the real time update of a list (Co-Auth) is not occurring. New entries made in one list are not showing in the same list seen by other users or in other browser windows in the real time (or even delayed) until manual refreshes are performed. Occasionally, edited entries using the same Form Customizer do update in real time or slightly delayed. Editing or entering entries in 'Edit in Grid View' or the out of the box customizer do update in real time.
However, for our uses, the out of box forms are not sufficient and live time (Co-Auth) of lists are necessary to allow live time monitoring of business-critical activities captured using SP Lists affecting multiple locations. This behavior WAS working pre-Spartan and were working in the early rollout of Spartan. In particular we are looking to fix for SPFx, however, the situation appears to apply to any non-out of the box forms.

Steps to reproduce

1. Create a new input form using a Form customizer and apply to a list
2. Duplicate that list into two windows
3. Make a new entry in one window using the customized form. Observe if the entry shows automatically or not in the other window. (it does not)

Expected behavior

SharePoint List expected behavior is for live time (Co-Auth) updating as changes are made regardless of the method of inputting new items.