It is only uncatchable because the defender illegally interfered with the receiver, preventing him from getting to a position to make a play on the ball. I have seen receivers do incredible things to get to a ball that for all the world appeared uncatchable, with and without impediment from a defender. The ball would have to be thrown into stands to be considered uncatchable.
If what you say was the measure of uncatchability, defenders would block receivers to the ground every time the ball went into the air.
This is a cutoff, and is a foul.
Robert