Thanks, that's really surprising. Credits get into ownership and payment, and I assumed some group of authorities would have that on lock, and would have pooled all their data since it's sort of in their interest to do so. Silly me I guess!

Spotify just pays the owner of the song (typically a record label) so doesn't need to be concerned with who created it. But yeah, even then, it's surprising the Spotify credits are so poor. Everyone forgets about Ringo!

Session musicians mostly only receive a one-time fee and no royalties, so would be irrelevant from a subsequent payment distribution perspective.