As you say, Saito always maintained that he was doing things "by the book" - pretty much the same way that things were done in 1938.
He was close enough to Yoshinkan that Gozo Shioda asked him to follow him there, at one point.
The interesting thing about Shirata, Tomiki, Shioda, and Mochizuki is that they all started before the war, when Kisshomaru started, but they all developed the styles that made them known after the war, just as Kisshomaru did.
If you ask me, the difference in "post-war" Aikido is less the product of differences in pre-war training by Ueshiba himself then it is the influence of Kisshomaru and Tohei on the Aikikai.
Well, it's all quite subjective about what anyone means... I have some friends who ae serious Yoshinkan instructors. They've come through town and visited the dojo and left saying it felt like home. I assume they meant how we trained and what the "heart" of it felt like rather than the form itself.
It's also important to recognize that almost none of the folks we are talking about just trained with any one teacher in Aikido and most did some amount of cross training.
I know everyone wants to put it on Kisshomaru and Tohei as being the big post war influences but deshi with whom I am most familiar don't look much like either of them and clearly emphasized elements in their practice that didn't come from either of them. Certainly the emphasis that Saotome Sensei and Nishio Sensei put on atemi waza and weapons work didn't come from either of them. Those elements were quite de-emphasized in the standard Aikikai version of the art. I also feel that Yamaguchi had more influence than is often acknowledged.
Anyway, the discussion is academic at best. Aikido is changing. The direction it is taking seems quite independent of the major figures that went before. No one will care in another generation.