There is judgment by the stat keeper involved too. That is why I used the term "Basketball Move". One dribble off a catch does not always negate an assist. Say a player is cutting to the basket and the passer throws him the ball, he takes a dribble on the run and scores, it is an assist.
There actually is no clear cut "rule" on assist on any level. Some coaches over report assists. I have seen players credited with assists by coaches for some pretty stange things, but what you describe is definitely an assist.