Instead it's about whether or not a person with a physical complaint handles their problem in a way that unnecessarily disables them. Which is a knife-edge when you say "unnecessary"; pain-management specialists debate hugely about this. But the purpose of this diagnosis is to ask: is the person adaptively dealing with their symptoms? Are they realistically estimating the risks and benefits of what they're doing? Are they, as far as they are able, living a happy and productive life? Or are their thoughts or feelings about the illness getting in the way?

I agree with this, except for the general ability of medical academics (in particular) to accurately judge whether or not someone is handling their problem in a way that unnecessarily disables them. And often doctors and allied health professionals do not know enough about complex conditions to be able to judge whether the patient is realistically estimating the risks and benefits.