Inherited Material Reference in the UI Builder disappears after adding a Material Property override for a child visual element

Steps to reproduce:

1. Open the attached project
2. Open the NewUXMLTemplate.uxml asset in UI Builder
3. Select the Button Visual Element
4. In the UI Builder's Inspector panel, expand the Material section
5. Observe that it contains an inherited Material reference
6. Press the + button to add a Material Property

Actual results: Inherited Material reference of why that happens

Expected results: Adding Material Property overrides for inherited materials is not allowed, or there is a warning/info message explaining why the same Material instance can't be overridden

Reproducible with versions: 6000.3.0b9, 6000.3.3f1, 6000.4.0b3, 6000.5.0a4

Can’t test with versions: 6000.0.65f1, 6000.3.0b8

Tested on (OS): Ubuntu 24.04, macOS 26.1