Only the name of the field inside Mp3Tag was changed from BAND to ALBUMARTIST. The tag of the mp3 keeps the same. What you have tagged before with a BAND tag has now a ALBUMARTIST tag. It is and was a TPE2 tag/frame and is interpreted as album artist by most media players.
ALBUM ARTIST is not affected by this change and keeps the same as before.
see here for a overview:
[F] Mp3tag v2.46a - 'Album Artist' Not Correct
If you still have the need to change tags (e.g. after using a not updated web sources script with the new Mp3Tag version), it's very easy. Make a action group with two actions.
1.
Action: Format Value
Field: ALBUMARTIST
Format string: %band%
Action: Remove Fields
Fields to remove: BAND