That should not happen, I have checked the code
If matches to a MusicBrainz Release then no issue since all artists on a MusicBrainz release have artist ids and we add artist/artists/artistsids and releaseartist/releaseartists/releaseartistids at the same time.
If matches to Discogs no issue we do not overwrite fields if already matched to MusicBrainz, if not already matched to MusicBrainz then when we add artists and releaseartists there is no attempt to match to MusicBrainz artists and add artistids.
If matches to Bandcamp then Bandcamp only supports a single artist, we try to match that artist to MusicBrainz and if match found we add artisid/rteleaseartistid if not we dont, but there is only ever one artist/release artist added. Does not overwrite fields if already matched to MusicBrainz.
If matches to Acoustid Album (which means matching a group of songs by Acoustid that do not link to MusicBrainz and finding common album metadata for all the songs on Acoustid) then Acoutid Albums only support a single albumartist/artist and we therefore we only ever add one artist and possibly one artistid, same for track artists. However, there does seem to be one bug we dont need to modify the artists or albumartists fields in this case although this should not cause you an issue since you don’t use these fields.
Then at save time there is one addtional tidy up where we try and improve the artist data for songs that have not been matched. This makes artist and artists fields consistent and trys to match the artists to MusicBrainz artists. If matches are found it can add artistids, but already it only does this if all artists on song could be matched to MusicBrainz artist
So I’m not aware of any issue, if you see an issue let me know.