Reproduction steps:
1. Create a project using Essentials Pathway template
2. Open the “Assets/_Unity Essentials/Scenes/-1_Starter_Scene“ Scene
3. In the Hierarchy window, select “MainCamera“ (Player > MainCamera)
4. Observe the Inspector window

Expected result: There is a Cinemachine Brain component
Actual result: There is a missing script warning

Reproducible with: 6000.3.0a1, 6000.3.0a3
Not reproducible with: 6000.0.54f1, 6000.1.14f1, 6000.2.0b12

Reproducible on: macOS Sequoia 15.5 (M1 Max), Windows 11
Not reproducible on: No other environments tested