Earlier quoted context omitted.
The same way you distinguish between feeling like having a problem and actually having a problem.
This is needlessly flippant and not really the same thing. Determining progress in a therapy setting is usually a collaborative effort between the therapist and the client. An LLM is not a reliable agent to make that determination.
Can anyone describe how to determine how a (professional, human) therapist is "a reliable agent" to make such a determination?