I agree, and will add one adjustment. With many grappling techniques - especially when focusing on least resistance - you can't expect to perform a specific technique against a resisting partner. If your partner knows what is coming, and uses what he knows, most grappling fails reliably. Same is true for punches, of course: if you know I'm throwing a jab, my ability to connect that jab goes way down, because all you have to do is defend that one thing. So, variable input and variable response options. If an opening almost never presents, that's a low percentage technique against that person. If that pattern continues with other people (especially if it continues with new students and people from other styles), that's probably a low percentage technique all-around...and only worth training if it's just too damned much fun to not train.