I wouldn't say that the Iwama folks I've trained with have demonstrated anything particularly unique relative to what I've seen/felt from other styles.
I never had the opportunity to train with Saito Sensei himself, so I wouldn't care to speculate on what he personally could do. But I see no evidence that his students received any more accurate transmission from the Founder than anyone else.
(FWIW, I'd say the same about students from Tohei Sensei's lineage.)
This aiki-mutt agrees with this and with Gerardo's post too.