Incorrect borders with .list-group-flush.list-group-horizontal

Prerequisites

• I have searched for duplicate or closed issues
• I have validated any HTML to avoid common problems
• I have read the contributing guidelines

Describe the issue

When using .list-group-flush and .list-group-horizontal on the same list group you get:

But was expecting:

Documentation seems to say that this is possible:

Add .list-group-flush to remove some borders and rounded corners to render list group items edge-to-edge in a parent container (e.g., cards).

I have seen another issue about putting a list group IN a list group. But that is not what is being reported here.

Workaround (how I made the second screenshot) is to add .border-0 on each .list-group-item

Reduced test cases

    <!-- a card with a link list group -->
    <div class="card" style="width: 18rem;">
      <div class="card-header">
        Featured
      </div>
      <div class="list-group list-group-flush list-group-horizontal">
        <a href="#" class="list-group-item list-group-item-action">Certificates</a>
        <a href="#" class="list-group-item list-group-item-action">Products</a>
        <a href="#" class="list-group-item list-group-item-action">AHA</a>
      </div>
    </div>

    <hr>

    <!-- a card with a link list group -->
    <div class="card" style="width: 18rem;">
      <div class="card-header">
        Featured
      </div>
      <div class="list-group list-group-flush list-group-horizontal">
        <a href="#" class="list-group-item list-group-item-action border-0">Certificates</a>
        <a href="#" class="list-group-item list-group-item-action border-0">Products</a>
        <a href="#" class="list-group-item list-group-item-action border-0">AHA</a>
      </div>
    </div>

Edit: CodePen created by @julien-deramond: https://codepen.io/julien-deramond/pen/rNoWJxg

What operating system(s) are you seeing the problem on?

macOS

What browser(s) are you seeing the problem on?

Microsoft Edge

What version of Bootstrap are you using?

5.3.1

Start with the reduced HTML test case or the linked CodePen, then trace the Bootstrap styles applied by .list-group-flush and .list-group-horizontal. Reproduce the border mismatch in Bootstrap 5.3.1 and verify that the combined classes render the expected borderless horizontal list without requiring .border-0 on each item.