While not directly what the OP/GP mentioned, sometimes it's worth noting that, if a person suffers from some symptom, they'll probably benefit from advice to (a group of) people who suffer said symptom. This is true regardless of whether said person is part of said group.
If Greg has issues concentrating, and someone says "I know people with autism can suffer from that, and they find stimming helps", then even if Greg is not autistic, they may be well served by that advice.
That said, they won't necessarily be well served by all advice (Ask your doctor for Ritalin!), and I'd personally rather leave it to themselves and their medical practicioner to diagnose/decide whether they're actually part of any given group.
If Greg has issues concentrating, and someone says "I know people with autism can suffer from that, and they find stimming helps", then even if Greg is not autistic, they may be well served by that advice.
That said, they won't necessarily be well served by all advice (Ask your doctor for Ritalin!), and I'd personally rather leave it to themselves and their medical practicioner to diagnose/decide whether they're actually part of any given group.