Yes, the inflexibility of GUE can be seen as a disadvantage. However, it can also be an advantage if you intend to proceed through a progression of courses. Each course builds on the material taught in the course before it, and relies upon that base to a greater extent than in other agencies' course progressions (or at least that is my perception). When you show up for the next course, the instructor can efficiently devote 100% of the time (which you spent a lot of money for) to teaching you the new material. You could have a new instructor for the next course, and the new instructor will not need to first determine what you learned or did not learn in the previous course. To achieve this, each course needs to cover the material in nearly the exact same way.