I don't think this is necessarily accurate. There's a great piece somewhere by George Ledyard (I'll see if I can find it) in which he writes that he can throw a yokomenuchi that even O-Sensei couldn't shihonage. Anyone can, if they know what technique is coming and set out to thwart it. That's not being realistic or difficult; that's creating a situation built on the premise that the attacker can read the defender's mind and the defender can't alter his course of action. Obviously, there's not much use to training for that scenario.
I myself used to work with an uke who, knowing that a kotegaeshi was coming, would stop his tsuki short and plant like a statue to deprive me of any momentum to work with. He would smirk at this as if he had beaten me, but the truth is that he had just performed an incomplete attack that (a) gave me no reason to defend myself and (b) left him open to all manner of attacks.
There is absolutely such a thing as a bad uke. Just like nage, uke has a job to do, and if he does it wrong, there can be no technique.
I think you are right. But I also think that sometimes it's hard for me as a 4th kyu to distinguish between difficult uke and bad technique. If I'm tori and I fail, it's important that I determine correctly whether it is caused by difficult uke or bad technique.
Sometimes it is a case of difficult uke. Sometimes the instructor corrects uke to change the attack or other aspects of ukemi. In many cases uke may not even be aware that he is being "difficult".
And with some ukes I just know that my first attempts will fail. Then they might give me some advice and sure enough, after that most of my later attempts will succeed. Every time we pair up, I know it will go like that. I think those are situations where both issues are in play. My technique has flaws and
they happen to be people who like to "lecture" me on my flaws. I do get frustrated by this on some occasions, but I keep this to myself. Normally I'm an "easy" uke (I think), but lately, when I think they're just thwarting my technique on purpose, I sometimes cannot help myself from thwarting them once in the same way when it's their turn (I know it's wrong that I do it, because I do it out of frustration, not to help them). It's not hard to make someone fail.
But for me, last week something shed new light on this issue. When the instructor had us practising shomenuchi ikkyo omote he stopped the class. Apparently he saw a tori muttering that his uke was being difficult (yes, I too consider that uke to be a difficult uke of the type I describe above). But the instructor said uke was not to blame in this case. It was tori making a very common mistake. He showed us the mistake and showed us how to do it correctly. It was hard to see the difference, but by telling us what he's doing while he's doing it, the difference was clear. It was a real eye opener to me.
On the other hand, the correction of the instructor (6th dan) seemed different in important details from the correction that this uke (2nd kyu) usually lectures me about, so I should not blindly trust the advice of uke, difficult or not. But perhaps this uke tried to tell me the same thing all along, he just could not get it across, I don't know.
So I learned a couple things:
- don't be too quick in blaming uke when your technique fails
- if you think you fail because of difficult uke, ask the instructor to correct your technique. it could be a great learning opportunity for you (and perhaps uke)
- those learning opportunities could be worth the frustration of difficult uke
I still like ukes better if they build up their resistance, so that in my first attempts they are easy to move, but in later attempts they become more difficult to deal with. I like this better than the other way around.