FWIW, I think Nishio's atemi (as demonstrated in the Yusuru Budo book and DVD series) is rubbish... and if I were to be more polite - at best, pre-school level atemi waza.
I guess you aim to tease in a friendly manner with those remarks.
I practiced many times for Nishio sensei, also at seminars in my own dojo, so I got to see and experience first hand his atemi skills. Simply put: in aikido, I have not seen anyone surpass his atemi.
And of course, he was also very learned about the exact target of each kind of strike.
I wonder about the expression "pre-school". You must refer to some distant time before the dawn of civilization. I don't know about that. But I know that Nishio sensei had studied all kinds of martial arts, including karatedo, in what I would call schools of them.
Moving on: As for the effectiveness of atemi, I find that rhythm has a lot to do with it. The element of surprise, of striking in a "syncopated" way, i.e. right before it is expected, and to do it paying attention to the movement of the opponent (either with it or right against it), and so on.
Atemiwaza is a martial art of its own, if studied profoundly. And true: when you know it well, you don't need any aikido techniques to follow up - but then, of course, it is no longer aikido.