Welcome!
Well, I'm not sure if a medical diagnosis would do him any harm. I think it depends on a lot of things. Maybe it could be good for him in the future. For example, I haven't been diagnosed when I was younger, and now I'm 25 and I really needed an official diagnosis, for many reasons. Or he can have a diagnosis and, if you don't feel confident, just don't mention it, as you do with yours.
This is just something for you to consider.
Again, welcome and enjoy your stay! You'll surely make friends here.
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Your Aspie score: 161 of 200
Your neurotypical (non-autistic) score: 45 of 200
You are very likely an Aspie
"A man is as free as he chooses to make himself, never an atom freer"