I didn't wade through all 7 pages...
The first problem is the title of the post. As "written" is MUCH different than "as recorded", or "as performed by So and So at such and such a time". It does depend on the song. And the SONG is >>NOT<< any particular recording nor any particular arrangement. I've been listening to an album of Wynton Marsalis and Eric Clapton together. They do "Layla" on there and the SONG is intact. Boring people won't like it because it doesn't have the lick Duane Allman created, but the song isn't that riff. I've also been listening to Aretha Franklin's live Fillmore West album. This is the one recorded with King Curtis' Kingpins including Jerry Jemmott. There's nothing on that album that lacks at all, but the bass parts aren't loving regurgitations of what Cobbill, Hood, et. al. played on recordings.
Note-for-note is a great learning tool. It's not interesting music to me at all. "They sound just like the record" is the last thing I want from live music. And here's what I've learned in my gigging live, playing almost exclusively cover material since 1976. The people in the bar don't care. "It's got a good beat and it's easy to dance to. I'll give and 85!" is what they think. Does the band sound tight, playing well together? They're happy.
Of course there're parts where one needs to play the line that people are familiar with. "Day Tripper" is one where you pretty much gotta play that riff. But, do you play it like Paul does in the same octave as the guitar or play it down with the open E string? I like it better like the record but it depends on the guitarist(s) and the nature of the band. I heard a pop-metal band do it and the bass played that riff down and it sounded great, and more "metal" than playing "correctly". And what about the lines under the II IV III VI V part? Does one really need to play exactly what Paul played there? And why does Bill Wyman play on both the verses and choruses of "Honky Tonk Women" live if the recording is sacrosanct?
The most vital and important music to me is the stuff where the bassline on "the record" is an interaction with the bassist, drummer, keys, guitars, vocalists, et. al. And the previous take may have had a much better bass part but the feel of the release take felt better.