Thanks very much for reporting this.
You’re right, there was a bug in which maps weren’t deleted from the database, as you noticed. It’s been fixed since beta 2.38.1.
If you like, you can try out the latest beta (2.38.3 as I write this) – it includes a lot of new features as well as that fix.
A future release will be converting the maps to custom post types, and I’ll include a cleanup routine at that time to remove all of the old map data (including the orphans).