He has to be on the active roster because they only had a certain number of days before they had to make that call. It doesn’t mean he’s ready to play in a game. He can be inactive until they want to put him out there. They are the ones watching him in practice.
This is a bad matchup for the Lions D. Okudah will be out and it’s already a weak secondary, they haven’t faced a passing offense like the bills during their 3 game winning streak.