Well, Blop, I wasn’t actually meaning to make that connection — poor communication on my part.
My understanding is that you don’t want to put pressure in the middle of the shaft right below the glans because of the dorsal nerve. That is, if you are gripping the shaft hard, you want to avoid that bit of it.
The warning against yanking on the glans itself, though, has something to do with the weak connective tissue between the glans and the shaft, if I recall correctly. Apparently it’s actually possible to rip that tissue apart and thereby cause major, major problems — if, again, my memory serves correctly :) .