How to reproduce:
1. Create a new 2D URP project
2. Create a Cinemachine Camera (any camera works) and select it
3. Add the “CinemachinePixelPerfect“ extension in the Inspector
4. Observe the “CinemachinePixelPerfect“ Component below in the Inspector

Expected result: A warning is shown that indicates that no main Pixel Perfect Component was found in the Scene (or on CinemachineBrain)
Actual result: No warning is shown

Reproducible in: 2.9.0-pre.1 (2023.1.0a1), 3.1.4 (6000.0.57f1, 6000.2.4f1, 6000.3.0b1)

Reproduced on: Windows 11 Pro, macOS 15.3.1
Not reproduced on: No other environment tested

Note: The main PixelPerfect Component is required for the extension to work correctly, so showing a warning when there is no such component detected is crucial for user experience