I'm sure they do it. I bet he's too busy clapping and spitting during the practice, he hasn't learned what to do in those situations himself.
Garrett actually strikes me as the type of guy that goes over every eventuality he and his staff can think of and then drills his players on the specific circumstances in what they call the "2-minute session" in practice. It's cliche and obvious after a season or so of hard knocks that they all do it.
Now don't think I'm defending Garrett. His players obviously don't know what they're doing in this instance and that ultimately speaks as to his ability to coach but quibbling how you want to run two minutes is besides as to what went wrong on the field last week and what issues Garrett actually has.
For example, in these threads, no one has really questioned Cassel's role in this. You want the head coach to execute this as opposed to the quarterback. Would you think it inappropriate to say Cassel looks weak on the field in general? Command of the huddle and formation. His rapport with line, back and receivers. How he moves and throws. It's all poor. I know if Romo called a perimeter play late he would have executed better. We've seen the team do it right with him a lot. If you want to give credit to Romo for that and not Garrett then fine but that is the where the real dysfunction on this offense is.
We haven't seen a quarterback this bad since Brad Johnson. I'm not sure he's better. Might have to go back to the corpse of Drew Bledsoe. When teams make the same mistakes regarding a position over and again it's troubling. It's an organizational problem undoubtedly.