It is an NFL average, but it also seems to be around the average for simulated season games in APF. Here's how to check for yourself:
- Go into season mode and sim a week. Take note of two teams who played each other.
- Go into the League Report to Team Stats. Scroll near the end of the stats list to two stats - Running Plays and Passing Plays. Add up the totals for each of the two teams that you noted on the schedule screen. That was the total number of plays in the game (excluding punts and other kicks, which are never counted)!
I've seen games with as low as 110-115, and as high as 130. But most of them seem to fall right around the 120-play mark.