I think it's a step in the right direction, though it will be interesting to see where the boundaries are drawn. Does YouTube count? What about gaming platforms like Roblox and Fortnite?
Edit: On further reading about this, I'm changing my mind. I can't see how this would be implemented effectively without some kind of age verification. Unless it's a meaningless Steam-style "What's your birthday?" question, that makes it far more troublesome for everyone's privacy. I can't see how it would get off the ground after so many Australians have had their data stolen already.
It would be great to see a Fediverse GitHub alternative. Obviously we have plenty of self-hosted software forges around, but I'm not aware of any decentralized network solution. Allow people to host repositories on an instance, but be able to search, discuss and contribute to repositories across the entire network. That way you'd get the benefits of a large programmer community without needing to centralize to a single company or organization. Maybe this already exists and I'm unaware.