That's not quite what QQ is saying.
Let's grant for a moment that K91 has psi powers. They only manifest randomly (say, an average of once a month over a year, but highly intermittently) but when they manifest, the results are compelling. He can predict the turn of 20 cards in a row.
Unfortunately, they've have to lock him in a room for months at a time, and test him every 20 minutes before they could hope to catch him when he's "on".
The unpredictability and unreliability apply to the ability, not to the results of the ability.
It may be hard to run test on this, but it can (could) be done. Science finds a way.
Thing is, we don't hear K91 explain how his ability works. He doesn't say whether he can invoke it at will. (He seemed to try and have it work, so that would suggest attempts to invoke it might work. And that means it might be worth a perfunctory experiment with a couple of witnesses), nor does he say how often it happens or how long it lasts.
For someone who a] has a gifted ability beyond the rest of humanity, and b] is gravely concerned over the welfare of so many others who are "suffering", we doesn't seem very interested in doing anything about it.