Multiple Buttons cannot be selected in a Toggle Button Group when in UI Stage and the option is enabled

Steps to reproduce:

1. Create and open a new project
2. Create a 'NewUXMLTemplate' and instantiate it in the Hierarchy
3. In Project Settings -> UI Toolkit, Enable in-scene UI Authoring
4. Open the UXML GameObject in UI Stage
5. Create a Toggle Button Group
6. Add a few buttons to the Toggle Button Group 
7. In the Inspector, enable 'Is Multiple Selection' checkbox
8. In the Inspector, click on multiple buttons above the checkbox and observe

Actual results: Multiple buttons can be selected

Expected results: Only one button at a time can be selected

Reproducible with versions: 6000.6.0b10, 6000.7.0a1, 6000.7.0a5

Can’t test with versions: 6000.0.82f1, 6000.3.23f1, 6000.5.10f1, 6000.6.0a7 (unable to edit UI Elements in Inspector)

Tested on (OS): Windows 11 Pro (25H2)

Notes:

• Not reproducible in the UI Builder