I agree. The potential doesn't increase the speed of the training. Just increases the limit the player can reach.
Well, there is no technically no limit to the level a player can reach -- not before, and not now. The rules state that potential slows training down significantly. There hasn't been any evidence up to now about whether this happens abruptly or gradually.
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."