You bring up an interesting point. I'm shooting a steel match this weekend and doing so with high cap mags. In trying to grab them out of my pouches, I do so with the same hand position as my normal production magazines. What I notice is, if I am not paying attention to getting things right, I have a greater tendency to bobble the reload because I believe there is more magazine above where my hand would naturally be with my production magazines. Conversely, when I use my standard basepads, I am higher up on the entire magazine which gives me a much greater hold and therefore control over the magazine which limits the amount of bobble and variable while trying to stuff it into the gun.
Just some random thoughts after reading your response.