What that does effectively is force people to join your faction to acquire a ship that is actually not described as belonging to your faction. By extension of your logic, as you are indeed a separate faction with your own ID, an IMG faction could equally prevent CR ID'd ships from acquiring IMG ships - and seeing as the infocards clearly describe these ships as all IMG, they would have even more justification to do so... but that sort of thing resolves nothing.
There are ships marked as IMG ships in your guard system, which, considering you now have a separate ID, seems to be by accident than by design. You can't prevent properly ID'd and tagged players (IMG that is) from entering what is for all intents and purposes an IMG Guard system to acquire that ship. It's not as if they are stealing an IMG ship....I mean they did build it after all.