Reproduction steps:
1. Open the attached project "ReproProj"
2. Execute the menu item “Tests > Schema Definitions”

Expected result: No Errors exist since the tested UXML content is valid
Actual result: Error is present "UXML validation error: Line 3, Position 6: The element 'VisualElement' in namespace 'UnityEngine.UIElements' has incomplete content. List of possible elements expected: 'Bindings' as well as'VisualElement' in namespace 'UnityEngine.UIElements' as well as'OverrideRow, ..." (truncated)

Reproducible with: 6000.0.62f1, 6000.2.10f1, 6000.3.0b7, 6000.4.0a4

Testing environment: Windows 10 Enterprise 21H2
Not reproducible on: No other environment tested

Note:
- This Error is present instead in 6000.0 and 6000.2 "XmlSchemaValidationException: Multiple definition of element 'UnityEngine.UIElements:VisualElement' causes the content model to become ambiguous."