I think thats also true for AMs. What they lack in dance ability the make up for by an intimate knowledge of their partners strengths and weaknesses. I just think the whole pro/am am/am difference is way overblown. Have you seen the quality of some of the pros? For some AMs they are liabilities not strengths.
Those less experienced pros usually do not have their students dancing in open events. If you talk about a teacher who is qualified enough to teach someone at that level, he probably knows what he is doing and can effectively show off the partnership's strengths and disguise weaknesses.