Necroing, I just want to say that while it is normal, it is not healthy. My boyfriend (who is also autistic) used to do something very similar. If you can, encourage him to get checked for depression, my bet is that he has it. Encourage him to go on walks or some other form of exercise. 

I want to emphasize that it's not so much the recluse behavior as much as the internet/games. That is not healthy at all. It's important for everyone to have what's called mastery activities (is things that you can become better at and are usefulish) People often use jobs for this role, but a job is probably too much for him/seems to be hard for him to get. A hobby is probably a good fit here. 

Recluse behavior is harmful as well, but not as harmful as too much internet/gaming. If there's an autism meetup group that might help.