If he sits two years one at CSU and one at NU would it not be a 3 to play 3? As he has used years 4 and 5 sitting out
You're both kind of right. He does have 4 years to play 3 seasons, but he'll have to sit 2019 (leaving a scholarship situation to walk-on) because of the transfer. He's not a typical 4 to play 3 since he can't use his redshirt whenever he wants.
At least in my opinion, calling him a 3 to play 3 implies that he's eligible next season and has three seasons to play.