Yes - this list is not correct. artist, artistsort, albumartist, albumartistsort are strings and not multi-value. It should have artists, ~albumartists, ~artists_sort, ~albumartists_sort in instead. And I think I agree about label and catalognumber (which match each other in sequence). releasetype is already in the list.

When I think (hard) about it, I can see that a medley could have multiple works in the sequence they are played, and that country and date are probably also in lock-step. So they should be added too.