Steps to reproduce:

1. Setup perforce server and workspace
2. Move attached TerrainTest project to workspace and open it using editor
3. Enable VCS in project and verify that Asset Serialization is forced to text
4. In top menu, click "Test/Add". This will create new Test.asset file and move New Terrain asset as a sub-asset of created object
5. Open p4v and notice that Test.asset is marked as <Text>

Doesn't happen with default terrain data file - only reproducible when it's moved to be a sub-asset.

Reproduced with: 5.4.1f1, 2017.3.1p3, 2018.1.0b9, 2018.2.0a2