After correcting artist tag, still not the same artist.

My collection of Ralph Vaughan Williams had inconsistent tags with three variations on the name, so in his folder I ran this scriplet.

artist='Ralph Vaughan Williams'
for i in */*.flac; do
    echo "$i"
    metaflac --remove-tag="artist" "$i"
    metaflac --set-tag="artist=$artist" "$i"
done

After that I rescanned and purged with python3 api/manage.py import_files 3c2dcdea-3901-47fe-a66f-fe28aa4c9da5 /mp3/Klassiek --recursive --noinput --in-place --prune and noticed I now have three artists, all with identical name.

How can I ensure these three get merged into one artist, or is this a bug?