I don't know if it's intentional filling in for songs they couldn't license or metadata matching gone wrong, but occasionally on Spotify a song on an old album

I don't know if it's intentional filling in for songs they couldn't license or metadata matching gone wrong, but occasionally on Spotify a song on an old album is replaced with an inferior remix from a newer album. Intentionally or not, history (what songs actually were on an album) gets edited unless you manage music files yourself. (The Apple behavior described in the article is way worse than what Spotify does, of course.)