A/V Protocols require students and instructors to expend a considerable amount of time and energy.
There is, of course, virtually no way for students using this technique to remain anonymous. Therefore, some students may by inhibited from trying, because they are afraid that they will do a poor job in working through the protocol.
Unless you are working in a field where there is only one accepted way of solving a given type of problem, students' protocols are likely to be diverse and difficult or impossible to compare directly.
Some students who are relatively good problem solvers are relatively poor at demonstrating what they know. This is a difficult sill for many to develop.