Currently no. But it's planned that it will: https://github.com/andrewrk/groovebasin/issues/30

All modifications to music files will be done in a separate temporary file on the same device and then rename(2) will be used to atomically overwite the old file. This way race conditions and power failure have no chance of corrupting the file.

I actually think the current behaviour is a good thing. I wouldn't want my original music files to be modified.

It's planned that all modifications to music files would be on a "suggested library improvements" pane. In other words, Groove Basin would propose actions such as writing the updated tags you just typed in to the music files, and the user would accept or reject these proposals.

So it's a compromise between wanting to take over and help you organize, yet respecting your file system.