> He began hiring in 2018.

2008 I think (from the wikipedia article). I met my now wife on the platform in 2013. I do think it counts, and it's important to note that even pre-AI, software has incredible leverage for small teams/individual people.

Of course it doesn't count. He is not a solopreneur at $500M.

So if I make a website that uses Nginx, Ruby, and Postgres, does that mean that I don't get credit for making it since I use other tools?

No, I just brought attention to the stack because it's not "sexy".