There was CLEAR visual evidence the ball came loose as it contacted the ground. Once it was determined Dez's momentum was taking him to the ground which was pretty obvious it was, he had to complete the process and he didn't.
No part of the 2014 rule book that says that. There is nothing in there about a player's momentum negating the catch process. In fact, there's nothing about momentum at all.
A forward pass is complete (by the offense) or intercepted (by the defense) if a player, who is in bounds:
a) secures control of the ball in his hands or arms prior to the ball touching the ground; and
b) touches the ground in bounds with both feet or with any part of his body other than his hands; and
c) maintains control of the ball long enough, after (a) and (b) have been fulfilled, to enable him to perform any act
common to the game (i.e., maintaining control long enough to pitch it, pass it, advance with it, or avoid or ward off an opponent, etc.)
The subsection you keep referring to applies
only if he's still in the act of catching a pass (meaning he hasn't completed a, b, and c above), and is only concerned with what happens when he contacts the ground.
If a player goes to the ground in the act of catching a pass (with or without contact by an opponent), he must maintain control of the ball throughout the process of contacting the ground, whether in the field of play or the end zone. If he loses control of the ball, and the ball touches the ground before he regains control, the pass is incomplete.
So if the ball comes loose when he hits the ground, but he is
not still in the act of catching a pass (because he
has completed a, b, and c), then "incomplete" is not an option. The only options are "fumble" (if he hasn't been contacted) or "down by contact" (if he has been contacted).
On the Dez play, the ruling on the field was "down by contact." We know it wasn't "fumble" because Dez regained control in the end zone and the official didn't give a touchdown signal. So the official must have seen the contact that sent Dez to the ground. Remember, "incomplete" is not an option. In order for Blandino to change the ruling on the field from "complete" to "incomplete," he had to go further back -- all the way back into the catch process. Now it becomes a question of completing steps a, b, and c.
Now it's about the catch process.