I’ve been seeing that lately. Part of it is probably missing the album artist tag on some compilation and soundtrack albums, but it also seems to group them all together so even various artist albums that didn’t have an artist of (person) listed get attributed the same person. I’ve renamed the group with a manual name to “Various” (Plex seems to use this instead of “Various Artists” to get the microphone artist image and album cover collage background) and then making sure to manually match stuff when possible to correct things.