Hmm, I think if you were able to plot the balls path on his throws, there is no way he's throwing downward on most of his passes, it's a physics thing... I don't know what the threshold yardage would be, but after a certain distance the ball has to have a ballistic trajectory http://www.convertalot.com/ballistic_trajectory_calculator.html. Which means up then down.
And, it is an issue for accuracy where a rainbow touch pass is required for timing purposes. Can't just rifle the ball in every situation, that's why he's considered inaccurate, because that's what he does. Hence the reason people are going on about his inability to be consistent on intermediate throws, which is kind of what the NFL is...