Saito was, of course, very close to the Founder. On the other hand:
Saito sensei lived 23 years with O sensei in Iwama, from 1946 to 1969 he had the privilege to train alone with the Founder on a daily basis,
Is not quite right. Especially after 1955 Ueshiba was in Iwama a third to half the time, or even less, at times. He spent quite a bit of time travelling - Osaka, Wakayama, Shingu, even Tokyo (especially towards the later 1960's).
Also Saito himself was working 24 hours on, 24 hours off - which means that he could train with Ueshiba at most every other
Put those together and you get an average
access of maybe two days a week over those 23 years (maybe less) - which is still quite good, but quite a long way from daily