I guess you mean the auto-playlist/radio stations play the same 20 songs?
I've had same experience as parent, Apple/Spotify/YT Music are interchangeable but for a few exceptions in who got a license to what, in which case YouTube wins because of bootleg uploads (Mos Def's Ecstatic comes to mind, ain't nobody got a license to stream that, but there it is on Youtube)
For my taste Yt music has almost everything, but spotify hardly has half my playlist.
I've found most of the music I listen to through youtube. So it's not suprising.
But I'd wager that almost every song on spotify is uploaded to youtube as a video. Then it should be available on yt music unless they have flagged massive amounts of videos as not musical.
