The fact is that Saito Sensei tought from O'Sensei 1936 book Budo, hence there was less change then some think. Personal this evidence is quite clear.
I think this is a bit of a misstatement. If I remember correctly, Saito Sensei was either unaware or had forgotten about the Noma dojo photos/Budo book until it was brought to his attention by Stan Pranin. Stan had found the book, and thought that it bore a striking resemblance to how Saito Sensei taught on a daily basis. After bringing it to his attention, Saito Sensei would apparently pull out the book as evidence that he was not doing Iwama-Aikido/Saito Sensei's aikido, but rather was preserving what he had been taught by OSensei.