Peter, you're evil, I like it. I suppose you're also a fan of the flip and sideways ukemis (with and without arms)...
Back on topic, no argument or anything to add with what's been put forward so far regarding relaxation for the projected kaiten-nage. As regards the head cradle/arm trapped version, I prefer to think of it as a controlled, relaxed splat rather than a ukemi. If I could roll out of it my partner's doing it wrong.