With the amount of publicity the case had gotten, a finding that Terri might not be PVS would have totally put the brakes on the case. Such a finding would render totally unjustifiable Michael's refusal to allow therapy to allow Terri to communicate. Although the Hugh Finn case set the precedent that even a clear and unambiguous desire to be given water can be overridden by a court's declaration that someone is incompetant to make such a decision, I don't think a court would have dare to have accepted that argument in a highly-publicized case.
It's also true that most of the media discussion centered on PVS as a necessary prerequisite to justify the natural death by dehydration. So opening that particular can of worms would have been even worse. I am not surprized in the least that the public is generally unaware of the present legal framework. Can't turn up the heat too fast, the frogs will jump out.
Whatever it is, it doesn't resemble justice unless the patient's wishes have been found correctly.