Those two songs are not normal 4/4 beat rock and roll but they DO demonstrate the incredible musical songwriting abilities Lennon/McCartney had.
Together they had a synergy that exceeded either of their abilities on their own.
I think they probably stuck by their official song sharing for this very purpose: to get double credit. McCartney and Lennon are weaker than Lennon/McCartney. Do we even know how much they collaborated after a certain point? By Sgt. Pepper at least they might’ve had less to do with the other guy’s final product than did George Martin.