You don't want an inflated reservoir tip because it increases the risk of breakage during intercourse. It has nothing to do with ejaculation and everything to do with friction between two layers of latex.
Short version: it's far easier for latex to tear when rubbing against another piece of latex, than as a single layer sandwiched between two pieces of skin. Thus anything that you do that increases the incidence of latex rubbing against latex increases the chance of breakage.
That's why you roll condoms on, keeping the material taut (to minimize chances of folds/wrinkles) and that's why you don't want air in the reservoir tip.
I don't see how a non-inflated tip would decrease latex rubbing against other latex. If anything it is increased. Take a non-inflated plastic balloon and rub it against your hand => plastic rubbing plastic. Now take an inflated balloon and rub it against your hand => no plastic touching other plastic.
> to minimize chances of folds/wrinkles
Have you used a condom? The chance of lots folds/wrinkles during usage is pretty much 100%.
Short version: it's far easier for latex to tear when rubbing against another piece of latex, than as a single layer sandwiched between two pieces of skin. Thus anything that you do that increases the incidence of latex rubbing against latex increases the chance of breakage.
That's why you roll condoms on, keeping the material taut (to minimize chances of folds/wrinkles) and that's why you don't want air in the reservoir tip.