what Detmer did, you have to be a serviceable player and have to have taken a significant number of snaps in real games.
Also, there weren't a lot of Ty Detmers out there even before the roster rule change -- Ty was an anomaly. And as BYU basketball fans know that when a prospect's pro comparison is an anomalous player, the future probably isn't bright (see Jimmer being compared to Steph Curry).