And these two attackers, with years of experience between them, said pretty much the same thing
I see two possibilities here.
a) The two were instructed to act as compliant ukes for a demonstration and describe the demonstrated techniques. Then editing and narration were used by the producers of the video to present the misleading impression that this was an actual sparring match.
b) The two were complicit in pretending a compliant demo was a sparring match.
Let's break down what is shown ...
1) The "karateka" grabs Shioda by the lapels like an untrained bully, does nothing else, and waits around for the aikidoka to perform a technique.
2) The "professional MMA fighter" throws a few tentative punches from out of range then, without any sort of setup to create a good opening, launches an out-to-in crescent kick. (Which is almost never used in MMA, for good reason.) When his target ducks out of the way, he allows the kick to turn him away from his target and makes no effort to recover his position. Then when Shioda pulls him down he makes no effort to defend himself on the ground and allows himself to be pinned in a position that any competent grappler could counter.
3) The two make no effort to work together intelligently. Instead they take turns throwing slow, sloppy punches without any set up and then leaving their arms extended at the end of the punch so the aikidoka can grab their wrists and apply a lock.
That's not a real fight. It's not a real sparring session. It's a compliant demo designed to make the demonstrator look good.
Shiota pretty much disappeared when they attacked him. This seems much more than simply moving off line.
Nothing in his evasive movement was particularly out of the ordinary.
I do think the way some Aikidoka move off-line is different. And sometimes it just feels surprising, because they don't seem to be getting out of the way, then they do.
Good boxers will do this. Good capoeristas too. I was taught to do the same in Bujinkan Taijutsu, but since that is normally practiced with compliant partners I don't think practitioners are typically as skilled at pulling it off in a live situation.