On a personal level I have to agree we you, at least partially.
My view on it is that Saito sensei was a pure product of O sensei's teaching from A to Z. And despite everything, he was probably amaong all students one of the few who had the closest relationship with M. Ueshiba. in French language "quotidien" has the added notion of familiarity, closeness, personal, close relationship, intimate, I guess this was worth being mentionned.
Besides, a quantitative centered approach may be not the most relevant view, after all there must have been some folks in Iwama who came training with O sensei every evening in the dojo, can it be said they received or understood more because of the quantity?
Somehow the 23 years span is an Iwama common place/meme that has been used often as some kind of proof or sign of some kind of "superior" transmission. In itself the figure is surely significant but my view is that it hides (or reveals rather) the quality
of the transmission, otherwise Morihiro wouldn't have been renamed and made guardian of the place O sensei called "home"...
(Cf. G. Homma in an interview or article, I can't remember)
Saito's not alone in this, of course, there are plenty of teachers whose students (and sometimes the teachers themselves) exaggerate their credentials. I've always thought that stating credentials that just aren't factually correct undermines the very real achievements of the people in question.
Of course - part of Morihiro's guardianship may have been that he was the only one there and was living on the property (and had been for some time) - that would make him the obvious choice doesn't it? And it doesn't require a hypothetical quality of transmission.
It get's trickier when you start talking about the quality
of the transmission - just about everybody has a reason or reasons why their particular transmission is better/deeper/more authentic than the next guy's.
Why not just forget about it and just base what we're talking about on what they actually did and showed?