If there was time for the coaches to run another 100 plays with the backups I will guarantee you they would use that additional time with the starters instead for more practice And certainly the Bills are not unique in thought process either, every team in the league would do the same. When you add in the limitations for practice it makes it worse. The extra time the QB coach spends with EJ,is that now less time he has to work with Orton?
I've read/heard that in a typical NFL work week, the back up QB gets around a half dozen snaps with the first team offense. And that statement was made prior to the latest CBA which further limits overall time, so may even be less.
For the same reason I always laugh at these posts from people who state the Bill's should draft a QB every year. Well then all you'll have is a bunch of inexperienced QB's who got zero playing time and never got better.