Reproduction steps:
1. Open the “ReproProject“ project
2. Open the “Assets/Scenes/SampleScene“ scene
3. Create a new PolyShape (Tools > ProBuilder > Editors > New PolyShape)
4. Observe the Scene View and the Console window

Expected result: The created PolyShape is visible and no errors/warnings are thrown in the Console window
Actual result: The PolyShape is not visible and the “Material count in the shared material list is higher than sub mesh count for the mesh. Object may be corrupted.“ warning is thrown in the Console window

Reproducible with: 6.0.1 (6000.0.1f1)
Couldn’t test with: 5.2.0 (2021.3.33f1, 2022.3.15f1), 5.2.2 (2021.3.38f1, 2022.3.28f1) (due to GPU Resident Drawer feature not existing)

Reproducible on: Windows 11 Pro (22H2)
Not reproducible on: No other environment tested

Note: When creating a Shape and selecting any of the shapes (Tools > ProBuilder > Editors > New Shape), the issue does not reproduce. Reproduces only when creating a new PolyShape