The Beatles' site is nice, but I have my doubts as to accuracy.
Check out "Love You To" for example...I defy anyone to find a bass guitar on that track, but Paul is listed. Also, I thought it was by now well-established that George contributed all the synth parts on Abbey Road, especially seeing how he had released Electronic Sounds, but Paul is listed.
(Side note: I have come to the conclusion that "Here Comes The Sun" is a George solo track, save for Ringo's drumming. Compare that pedestrian bass line in tone and feel to everything else McCartney did.)
I always knew John played bass on several Beatles tracks, in particular "Let It Be," "Back In The USSR" and "The Long and Winding Road." It is news to me to hear that he's playing bass on "I'm Looking Through You" and "Rocky Raccoon" and, given the style of play, I don't believe he played bass on "Helter Skelter."
The tracks where Harrison is listed as bassist are interesting: "Sgt. Pepper (Reprise)," "Hey Jude," "Back In The USSR" (actually a 6-string bass), "Honey Pie," "Golden Slumbers," and "Carry That Weight."
Didn't Lennon used to say he played everything on "Ballad of John and Yoko" except drums? I forgot to check that one out.
Anyway, compare McCartney's style with the basic root-five stuff his compadres contributed and see if you get a better appreciation for Macca's bass skills.