He stays locked, but you can't coach him out of being top-heavy. You can't coach him out of waist-bending. You can't coach up lateral agility. From what I've seen on all of the tapes I've watched, he lacks that in spades.
The Gallery comparison comes because Gallery was also a left tackle at Iowa who was forced to move to guard because of his atrocious pass-protection skills. Like Gallery, Scherff is also a great straight-line athlete who can get to the second level in the running game. Like Gallery, Scherff struggled mightily with fast and/or powerful defensive ends.
And again, if I'm taking a guard in the top fifteen (which is where Scherff will likely land), I want to make damn sure that he can already do everything in college and not hope for the best that porous run-blocking/pass-protection will automatically improve once he moves to guard. Hence, I would only take someone like Warford, Shields, or Hutchinson - guards who had already proved themselves adept at everything and had dominated every opponent who was below their talent level.
If you want a tough, mauling OG, then La'el Collins would not be a bad choice in the slightest...but you'd have to trade out of the top fifteen for him. Or take A.J. Cann in the second round, who can also double as a center.