Many folks see the big stats that lone good play, but there is a bigger picture.
1) Judging a player with stats if the player has a great offense that gives the qb the big play.
Look at Washington State's Gordan, Gordan set records in the Pac 12, but no one is calling for him for to be the 1st qb picked.
2) Judging a player's stats on weak teams.
Josh Love from SJSU faced not very many good teams and has the 3rd most passing yards, and no one will have Love on the top of the list of qbs.
3) Play design don't matter.
Sanchez and other qbs like him have had great offenses with plays that made the qb's life easy since the play could decide for the qb, but the issue is that will never happen in the NFL.
4) Time in the back-field don't matter.
The o-line can be so good that someone like Mayfield had some amazing stats in college partly due to the 5 seconds of time to throw, so Mayfield is struggling to adjust in making under 3 second decisions.
This one is tricky, but I have notice over the years people get caught up in doing the whole qb prospect 1 is better qb prospect 2 then qb prospect 1 must be good. Qb prospect 1 might end up to being a better back-up qb, but this does not mean qb prospect 1 is good.