To clarify: finding cognition in a five minute exam would be more meaningful than failing to find it in an hour. Doctor Cranford, one of Michael's "doctors", has an amazing knack for making PVS diagnoses even for patients who can move about with a wheelchair. Why would Michael hire that sort of "doctor"?
Throw it out then. Throw out anyone who's possibly biased by the fact that they've been hired by one camp or the other, and stick with the court-appointed doctors. You still wind up in the same place.
Does one have to be an art expert to recognize that a Rembrandt landscape which features telephone poles in the background is a fake? Or to know that an art expert who takes five minutes "authenticating" a painting is himself fake?
If it were that clear-cut, I don't think we'd be having this discussion.