do you know what an over throw is? (you should watching Stafford) That ball was on the money...if anything it was slightly under thrown since the WR had to slow down a bit to catch it. I have no idea why he went to the ground...it looked as if he really didn't need to go to the ground at all.
It was slight and yes momentum carried him too. Not a drop though. Not labeled a drop by anyone and clearly a tough catch.
Like I said, you know damn well that ball isn't caught very much on those type of throws. A play like that probably has the lowest % of getting complete.