Ok, but the clinicians and SMEs they'd be working with would be covered entities, and that would make him a business associate.
If his system records a symptom they have, attaches that to a stable piece of PII, then refers them to a covered entity for treatment, that makes the symptom, the PII and the treatment referral all PHI and therefore bound by HIPAA.
He would need to have a contractual relationship as a vendor or service provider to a covered entity to even maybe qualify as a business associate. Does he have that? I doubt it, this just seems like one person’s side project.
If his system records a symptom they have, attaches that to a stable piece of PII, then refers them to a covered entity for treatment, that makes the symptom, the PII and the treatment referral all PHI and therefore bound by HIPAA.