I would agree. The receiver, to his credit, was obviously aware of the game clock and took legal advantage of his opportunity to reduce the time remaining for his opponent. There is no requirement to score, as quickly as possible, and it is a legal opportunity to tactically consume time.
Had there been any demeaning gesture, either to the opponents, or in an egregious effort to bring exaggerated attention to himself he would have been guilty of an UNC foul. In the absence of either, there doesn't appear to be any such foul committed.
Of course, what happened thereafter was NOT caused by the application of a foul, rather was the result of allowing the opponent to score again.