The place and direction of the contact (a clear grab and hold, or carry as the case was) and the location of the interception both lead me to the conclusion that DPI was correct. The receiver may have been prevented from either fighting for the ball or contesting the interception by the contact. Now, had that been a simple arm bar and nothing else, then yeah, I might have been persuaded to pick up the flag. But if you look at the replay, it was the rule book definition of tackle.
In order for it to be uncatchable when the ball doesn't leave the field of play, it has to be REALLY uncatchable.