Reproduction steps:
1. Create a new project
2. Install the “com.unity.terrain-tools” package
3. Create a new Terrain GameObject in the Hierarchy (3D Object > Terrain)
4. Select the newly created “Terrain“ GameObject
5. Go into the Terrain Component’s settings tab in the Inspector
6. Observe the “Draw Instanced“ option

Expected result: “Draw Instanced“ is enabled by default
Actual result: “Draw Instanced“ is disabled

Reproducible with: 5.3.0 (6000.0.57f1, 6000.1.16f1, 6000.2.3f1, 6000.3.0b1)

Reproducible on: M1 Max MacOS 15.5 (Tested by CQA)
Not reproducible on: No other environment tested