I have in the past pondered the working of Arisaka rifles.  I think the reason they have the somewhat odd shaped knob, and the reason we find them awkward to work is that the Japanese were taught to work them with their palms.

I am going to try the bolt handle grip some before Camp Perry.  It gives me a pull back into my shoulder that's hard to get while trying to grip the thin wrist of a 92/96.  I cut the end of my middle finger off many years ago in a paper cutter, it conforms to the curve of the Krag trigger pretty good.  I have about half dozen local matches I can try it in before Perry, matches where I'll only have 60 seconds to get 10 shots off.