That’s def the rules for the nba, they will draft a player and sit on the rights indefinitely and the player can’t enter the league unless it’s with the team that drafted him.He can, but can't get drafted again by the Bengals. He'd also run the risk on dropping in the draft and losing out on millions from that draft slot.
No fkn clue about the nfl though, we haven’t had this happen in modern ball.