Missing namespace errors are thrown when the 'SURFACE_CACHE' scripting define is enabled

Steps to reproduce:

1. Create and open a new URP project
2. Open Edit -> Project Settings -> Player -> Script Compilation
3. Add a "SURFACE_CACHE" Scripting Define Symbols
4. Press "Apply"
5. Observe the Console

Actual results: 4 'missing namespace' errors are thrown
Expected results: No errors are thrown

Reproducible in: 6000.6.0a2
Not reproducible in: 6000.0.72f1, 6000.3.12f1, 6000.4.1f1, 6000.5.0b2, 6000.6.0a1

Reproduced on: Windows 11 Pro (25H2)
Not reproduced on: No other environment tested

Notes:

• One of the errors read:
  • Library\PackageCache\com.unity.render-pipelines.universal@f5f4d476217d\Runtime\RendererFeatures\SurfaceCacheGIRendererFeature\SurfaceCacheWorldAdapter.cs(286,18): error CS0246: The type or namespace name 'TerrainChanges' could not be found (are you missing a using directive or an assembly reference?)
• Each other error is a variation of the first one with 'TerrainChanges' or 'TerrainDataChanges' namespace missing