I was assuming that he'd maybe felt Mochizuki at some point. If so, you'd think that if he couldn't do what either of them (Mochizuki or Ueshiba) were doing and was being told he wasn't doing real aikido that he'd at least have to know. Especially for one who seems so hardcore about the training. Maybe it's a cultural thing?
and I think we know what the difference is now.
Context, context, context is the rule for the Japanese.
Quoting his answer:
I was told "What you guys are doing now isn't real Aikido". That's really a terrible thing for someone who is such a senior to you to say and I really resented it, but I was told, "This is Aikido" by O-Sensei and I have protected that as I continued in my training. I was told "After the war O-Sensei just changed the techniques however he pleased", so I thought "After all, people from before the war are different".
You have to wonder what the context was for Mochizuki's statement. What the context was for Ueshiba's statement. Just what did Ueshiba mean by "This"? And, more importantly, when each was done.