A lot of assumptions here that 1) Yoko "is" her singing, (to not like it is to bash her), and 2) that she has no sense of humor about herself. But if you recall humor was the first thing anyone knew about her, not self righteous offense. This came from John about their first meeting and her art work.
Which parts? I noticed the 90s version of Dera Duhn from the Threetles interview was processed to sound lofi, to sound like a 60s version maybe?
One observation (it may be have said before); there are moments when John and Paul talking to each other and...they seem to have a language that seems unintelligible for outsiders...the 'hidden microphone' talk in the canteen is strange and rambling...there's also a moment after 'Dig A Pony' where they seem to be associating on each other's words... A proof (if proof needed) that these guys were close!
First of all, no, you don't need to see her pulling a face as she does in that earlier scene as preparation for her later singing. And again that's not an example of "Chekhov's gun"; it's the inverse of it.
Of all the Beatles songs considered for a single, this one amazes me the most that it was not released. But I guess when you have both "I want to hold your hand" and "It Won't be long", something has to give.