I am curious about the methodology they apply to such patients.

I'm not that deep into the rehab subject yet but I'll get there in a few months or years.

I guess you have to analyze the signs in the patient's behavior to confirm if the behavior is genuine, right?

Yes. Even if the patient has good insight about their problem, it's no guarantee that they make good judgments. It's like seeing someone admitting cigarette smoking is bad for their lungs yet they persists smoking. Although good insight helps with the rehab or treatment since the patient acknowledges the problem, it does not always follow that they do the right thing.