When using /sburbpredefine define with two incompatible land types, it'll silently replace the title land type with a compatible one. Likewise, if defining title with an incompatible title land type, it'll silently replace the title with a compatible one.

We could try taking a softer stance on incompatibilities, allowing them to be set with a warning.
Or we could take a harder stance, failing to predefine with feedback to the command user.