Reproduction steps:
1. Open the attached “TestGridU6” project
2. Open “Assets/Scenes/SampleScene” Scene
3. In the Game View control bar, turn off the 2D option (switch to 3D)
4. In the Game View, observe the Cube
Expected result: The Cube is not see through
Actual result: Grid lines behind the Cube are visible
Reproducible with: 2021.3.50f1, 2022.1.0a1, 2022.3.60f1, 6000.0.44f1, 6000.1.0b12, 6000.2.0a7
Reproducible on: macOS Sequoia 15.3.2 (M1 Max), Windows 11
Not reproducible on: No other environments tested