It does strengthen the muscles involved, and any strengthening will bleed to other positions of the hand. But he's right that the position being strengthened most by fingertip push-ups is pretty far from the position used in gripping. I still use it - you just have to know the limitation and be okay with it. It likely also stresses the support muscles in a different way, which would be helpful for grappling.Perhaps you are correct and I wouldn't be surprised if you were; I cannot claim to know everything. But from my experience, it has helped me a lot with my Traditional Jujitsu and my grip there, and I don't do any other exercises for grip unless you count pull ups. I also went to physio after a full recovery of some injuries and I was told my grip is excellent (don't meant to brag, sorry) for my age.