I don't think you fix a nervous thing (hitch or twitch) through game reps. The game reps add more reason to be nervous, disappointment, etc.
Game reps can teach reading the field/defense, going through the 1st, 2nd, and 3rd reads, changing the play at the line, etc. No QB learns that type of stuff without game reps.
On the McAfee show, BB said the important thing is once you start the QB, you can not pull him or you might ruin him. Tua recently criticized Flores, who repeatedly pulled Tua, and "being pulled" still bothers Tua years later.
Drake is only 21. We think of all rookie QBs as being equal, but Drake is very young. Drake did not develop extra emotional confidence by staying in school so the Pats better be careful.
Mac was 24 for instance. At 24 sitting for a year or two makes less sense. At 21, sitting awhile would not hurt.