The projectnames are the same but they are seen as different projects. I can load one or the other and make changes. I still think it shouldn't be possible to import a project while one is already being imported.
This morning i tried to reproduce this behavior by importing large aia projectfiles but now I couldn't make it happen.
I tried your problem by starting a blank project named 'test'. Then, I exported it and imported it back to MIT App Inventor without deleting the old project. It showed a popup:
BTW, I use https://ai2-test.appinventor.mit.edu
Yes, I did it again with drag and drop. With a larger project that took a little longer to load. When I imported from the menu, I was able to import 2 times but the project was only one.
Oddly enough, they can be modified independently. Apk builds fine and they all have the same package name. Since everything works, why forbid the storage of projects with the same nave?