I do have the impression that there's now more emphasis on the connection and friendship between the four of them.

Yes, exactly this, and word on the joy! (MLH in a memorable passage in his memoirs about them when he first met them - which was years earlier when he shot a short promo for one of their songs - calls them "the gods of joy" for the decade.

I hear you on Debbie the receptionist. Will have to look up Chris O'Dell's memoirs again when I can, because she worked for Apple at the time (she's one of the people on the roof, in fact), and writes in some detail about some of her fellow workers).

I'm fascinated that this feeling also emerges from footage Jackson didn't direct - that selection and editing can show so much personality

Yes, it really underlines why a director is an artist in their own right (well, can be, of course there are lots of hack directors, too), even or especially with documentary material (i.e in a scripted movie you'd have several takes on the same scene to pick from, with the actors repeating their performances, but in a documentary such as this one, if you don't have a particular event captured, than that's it.