Steps to reproduce:
1. Open the attached project “IN-138905”
2. In the Project window, open “Assets” → “Scenes” → “SampleScene”
3. In the Hierarchy, select “TestTerrain”
4. Right-click the “Write To Terrain” component and select “Update Terrain Heightmap” from the context menu
5. In the Scene view, move the camera and observe the performance
6. Right-click the “Write To Terrain” component and Select “Sync Terrain Heightmap” from the context menu
7. In the Scene view, move the camera

Actual result: When the “Update Terrain Heightmap” is selected the performance of the Editor is significantly hindered
Expected result: When the “Update Terrain Heightmap” is selected the performance of the Editor stays relatively the same

Reproducible with: 6000.0.56f1, 6000.0.74f1, 6000.3.14f1, 6000.4.5f1, 6000.5.0b6, 6000.6.0a4 (77e2e2eea1be)
Not reproducible with: 6000.0.55f1

Reproducible on: Tahoe 26.4.1 (M1 Max), Windows 11 (User reported)
Not reproducible on: No other environment tested

Note: The User states that the performance difference is noticeable on Profiler