let me just expand on my statement. lol Sensei has had me purposely grab him and lock down in this manner specifically so he can show me and other students that this does indeed create weakness elsewhere. I never bring that grip out unless the person I am working with, usually the black belts, specifically asks for it. For us lower ranks that grip is simply not going to really help their, or my training, when we are still trying to learn the basic excercise.
Having had the experienced of being sent flying in spite of this kind of grip several times, I can honestly say that, yes it sure does create weakness elsewhere.