For the record, a hikikomori makes a video game? Wow. I wish I can do that. It's a matter of effort, of putting a foot in one another. The thing is, developing a video game and releasing it to the public is inherently a social activity, unless you write the code only for yourself.
Things are happening. Playing video games which is what creates despair for me. Nothing happens outside of that video game. Don't get me wrong, playing video is a lot of fun, but it isn't beneficial when there's too much of it.
The currently accepted definition is however merely:
* spending most of the day and nearly every day confined to home,
* marked and persistent avoidance of social situations, and social relationships,
* social withdrawal symptoms causing significant functional impairment,
* duration of exceeding six months,
* no apparent physical or mental etiology to account for the social withdrawal symptoms.
Under these criteria (quoted straight from the linked Wiki article), a person working from home office with no contact can also become a social recluse, even if it's certainly a different experience then what you've experienced
Personally I think your definition doesn't actually work, tbh. Where do you draw the line for "no participation in society"? Wouldn't that mean any interaction? Now they can't even order through a web portal, can't comment on social media like reddit etc. You'd need to create an incredibly controlled environment to make that viable, which would remove the self-imposed aspect of it.
Even the article you're commenting on has a hikikomori releasing a game project after several years. He wouldn't be one according to your definition either, even though everyone that knows about him IRL would absolutely call him one.