The problem is that in most cases there isn’t “actual” sheet music, i.e. they weren’t playing precisely off of sheet music in the recording sessions. They had anything from written-out music that they riffed on, to sketches or chord charts, to just having it all in their head.

Yeah, I kinda figured this was the reason there isn’t “real” sheet music for modern songs. It just sucks that it seems like a lot of these books just say “fuck it” and write out a simplified version that doesn’t even sound like the original instead of attempting to get the correct notes even if the timing would be “off” because of the way the song swings. Sort of like good guitar tablature, where it might not take the timing into account at all but at least you know which notes you should be playing to get the right sound and it’s usually commentated to help give insight to how the artist played it. Thank you though, I’ll take a look into transcription books when I get home!