It'll just pick the first data that matches that it finds in the folder. And yeah, I wish Unity had a bit more control over that when updating assets, but I feel like I have to have the defaults I already have included, or they'll just never be used/have to be created over and over.
I think you should be safe to delete the originals and make new ones, and then just be careful when re-importing in the future. If you were to import a double, you'd just have to delete the extra for STM to work as expected - it'll just go through the folder and find the first file that matches the requested data