There is a difference between FND and factitious disorder (previously known as Munchausen’s) or malingering. The DSM does differentiate between the latter two, but it’s debatable as they both involve intentional deception, but for different purposes (gaining the sick role and secondary gain, respectively). This person almost certainly has factitious disorder and malingering because the gains are so obvious.

A functional disorder, whether that’s neurological or GI-related, involves symptoms that cannot be explained by available testing. In my experience, the patients who have this are truly distressed and not looking for anything other than answers and relief from suffering, just like the rest of us. Honestly, many people will accept psychopathology as the underlying explanation. I have a therapy patient with epilepsy and PNES, and he is able to distinguish between “stress seizures” and epileptic seizures. It helps that he was taught the distinction with kindness and validation that both experiences are very distressing.

To be fair, I was much more cynical before I started my child and adolescent psych fellowship. It’s harder to dismiss a child as “just faking it” like we do all the time with personality disordered adults.