The Pitt AO told us that any time in August was good, but after that, the earlier the better to demonstrate interest, and to be considered in the earliest rounds for merit scholarships and highly selective programs.
Perhaps you think of Pitt as relatively “easy admission,” but that is just for admission to the university in general. Pitt has some very competitive programs with limited spaces, and merit scholarships which are doled out incrementally and at some point they run out.