There is more than one way to skin a cat. Stewart will play not because he can space the floor horizontally, but because he can space the floor vertically as a lob threat. He will also be a monster on the offensive boards and those could turn into wide open perimeter 3s via the kick out, or dunks and put back inside by him.
According to BT, among all High Major players who played at least 18% of his teams minutes this year, Sean Stewart had the 2nd highest OR%, ahead of Zach Edey who finished 3rd. With the same criteria, he had the 18th highest DR%, If he can maintain those levels of production, and improve his defensive awareness in the off season. I don't see how Scheyer keeps him off the floor.