The craziest thing of all is that one of the techniques that you can better place against a realistic opponent is the one I would have judged less fit: nikkyo. If you struggle your way to a wrist, nikkyo just seems the most spontaneous torsion to try.
Discussion boards are so useful because they also give you an opportunity to think, besides many others.
I think the reason an otherwise complex technique like nikkyo seems to come spontaneously against a heavily dynamic attacker depends on this: you attempt to irimi laterally to one arm.
If you manage to outfast your adversary who immediately attempts to face you squarely again to go on hitting you, at the moment you place your hands on his arm (say right arm, and you're lateral on his right side) your wrists are going to land there in extension
(outstrech your arm, now raise your hand upward so that its back facing you: anatomically
, that's an extension
of the wrist).
At that point, once grabbed the arm, the spontaneous movement is precisely that of producing your wrist flexion
(the opposite movement) because you just have a residual extension radius amounting nearly to nothing: you can't go that direction (that would prepare an uke upward palm for a kotegaeshi) any further.
Ath that point your next flexion, of course, produces exactly either a nikkyo set or goes for the sankyo.
I think this may account for why nikkyo seems to prevail, for me - I think.
It would be very unnatural going lateral and grabbing uke's arm with flexed
wrists - that would mean grabbing from within, a position that makes you even more vulnerable and without any possibility of adding the momentuum of your chest leaning forward - which latter instead fits pefectly extended wrists grabbing an arm and then rotating internally with flexion.