Editing Terrain prefabs directly from a custom editor window. Updates not applying to scene instances.

I am using a custom editor window to automate changes to a 4x4 grid of terrain prefabs. The problem is that some Terrain variable changes do not seem to propagate out to scene instances immediately.

For example, here you can see that when I select the prefab in the project folder the pixel error value has been set to 5 via my editor window, but below that is an image showing that the prefab instance in the scene still has the old value of 2 for the pixel error.

However, after entering play mode once the values then seem to update properly in the inspector (and reflect those changes in the scene view as well). Is there a way to force this update via code rather than needing to enter play mode?

I get the reference to my terrain GameObject prefab in the project folder using the AssetDatabase.LoadAssetAtPath method and call the following function on that prefab:

 void ApplyTerrainSettings(GameObject terrainGo) {
 
         //Terrain Settings
         basemapDistance = 1000;
         castShadows = true;
         detailObjectDensity = 1.0f;
         detailObjectDistance = 70;
         heightmapPixelError = 5;
         
         //Terrain Data Settings
         terrainWidth = 2000;
         terrainLength = 2000;
         terrainHeight = 4250; //Combine for terrainData.size Vector3
         heightmapResolution = 2049; //Heightmap Resolution
         detailResolution = 1024; //Detail Splatmap Resolution
         detailResolutionPerPatch = 16; //Detail Splatmap Resolution Per Patch
         alphamapResolution = 2048; //Control Texture Resolution
         baseMapResolution = 1024; //Base Texture Resolution
 
         Terrain terrainComp = terrainGo.GetComponent<Terrain>() as Terrain;
 
         terrainComp.basemapDistance = basemapDistance;
         terrainComp.castShadows = castShadows;
         terrainComp.detailObjectDensity = detailObjectDensity;
         terrainComp.detailObjectDistance = detailObjectDistance;
         terrainComp.heightmapPixelError = heightmapPixelError;
 
         terrainComp.terrainData.size = new Vector3(terrainWidth, terrainHeight, terrainLength);
         terrainComp.terrainData.heightmapResolution = heightmapResolution;
         terrainComp.terrainData.SetDetailResolution(detailResolution, detailResolutionPerPatch);
         terrainComp.terrainData.alphamapResolution = alphamapResolution;
         terrainComp.terrainData.baseMapResolution = baseMapResolution;
 
         terrainComp.Flush();
 
         EditorUtility.SetDirty(terrainGo);
     }