I understand your point of view Kevin, because it is hard to get the nerve all the time. Especially when its that burly new guy with hairy forearms who's about twice as large as you lumbering towards you mammothlike.
Before attending this one singapore camp, I used to apply yonkyo just like I was taught in my first dojo. Religiously find the nerve and cut down like the sword. It works in my dojo at least (1st and 2nd).
Then in singapore i was shown that you didn't have to pursue the nerve directly. Holding the forearm right and extending into the cut works better then my traditional, inside of knuckle and forefinger straight style. And it helps that now you are thinking of taking uke's center rather then having your mind focused on that one nerve spot. Don't get me wrong, my traditional style hurts a lot, but it involves too much forcing as this singaporean sensei said after applying it on him. Then he grabbed me and effortlessly splatted me on the floor. So i have no reason to doubt him since.
But what you've said in previous posts has been interesting to me, cause I like to dabble in pressure point training. Only there are no commercial instructors here in my place, so i get my kicks from the books. Which is not enough, (try learning aikido from books say). Maybe, just maybe you should ask a real PP fighter to test his skills against yours. Perhaps then, it might give you hints as to whether the stuff works or not.
As for me, I think yonkyo isn't entirely about nerves, nor is it entirely about body mechanics. Like all aikido techniques, it encompasses a lot more and that's why the simple looking ikkyo is called a 10 year technique.