To illustrate, here is a screen shot for a clinic presentation I am doing for Glazier in Dallas:
For example, the "Cover 4" on 3rd Down we get might be different than in the Scoring Zone (my other Glazier clinic topic). Thus, it is SO important to be able to vary the offense, not necessarily from a pattern perspective, but from how the coach uses Navigation Tags to give the QB direction. (By the way, the Navigation Tags and certain structures might have evolved as well, as a system is a living, evolving thing).
As an illustration, one thing that evolved for us last spring was how we employed the TRAIL route. In order to better take advantage of the brackets defenses were trying to build, we sped up the rhythm of the pattern, combining it with a SLANT to get open or clear, followed by the trail: