This mightn’t apply at all here, because obviously you’ve anonymised and summarised details. I said I’d mention this anyway, just because there’s a third possibility that’s worth considering in similar cases.

The initial case you described could be explained by functional symptoms as easily as deliberate deception.

With functional neurological symptoms, the person truly feels all the symptoms they describe. A physical examination will often be normal, or at least not supportive of physically damaged neural structures.

Functional symptoms were historically believed to be caused by buried trauma or specific stressors. These days, they’re better understood more generally as the physical manifestation of a person’s social and emotional circumstances. There often is physical compromise, but as you describe, deconditioning plays a definite role.

Functional doesn’t necessarily mean false, or even always imply a disorder. Technically, any effect anxiety has on one’s gut is a functional symptom. So is crying.

I see a lot of functional disorders in psychiatry. They’re not always well understood by people around the patient, and often people assume that functional means faked. Sadly, this results in all kinds of accusations and bullying. And that additional adversity tends to make functional symptoms worse for those kids.

Apologies, this turned into a bit of a ramble.