How to reproduce:
1. Create a new 2D Unity project
2. In the Hierarchy, right-click -> 2D Object -> Sprites -> Any Sprite GameObject
3. In the Inspector, on the "Material", open the Object Picker
4. Find the "Default-Diffuse" Material and observe both of its previews

Expected results: The previews match
Actual results: The previews don't match

Reproducible with: 6000.0.73f1, 6000.3.14f1, 6000.4.4f1, 6000.5.0b5, 6000.6.0a4

Reproducible on: macOS Tahoe 26 (M1)
Not reproducible on: No other environment tested