That's not a bug, but a feature. Unless desktop files are written in a way that they're excluded in some DE (using a custom key to do so, mind you), all DEs will show the item. You can "fix" this behaviour by installing just what you want ;)
- bug#39459: Multiple terminal programs to choose from, n... Scott C. MacCallum
- bug#39459: Multiple terminal programs to choose fr... Leo Prikler