Once it finds a match, it will show you a comparison of the tags for each file before and after. Maybe that's what you saw. As far as I know, it only writes the tags and renames the files once you hit save. If there is an option to write the tags before you choose to save, I've never seen or used it. You can of course choose to not rename the files and just fix the tags.

[–] limelight79@lemm.ee 1 points 8 months ago

Yeah I think the interface confused me at first, I figured it out last night. Basically you are matching files in the top left to the top right (either automatically or manually). Once it matches it shows the before and after at the bottom, then click save to update the file. Useful!

I was having issues getting Jellyfin to update some data, in particular release date/year, even after using Identify on them and pointing to the correct album. I had to manually update that info for several of albums. Maybe the incorrect info in the mp3 tags overrides what it gets from the internet. That would explain it.