Isn't that exactly what he's doing with x.ai? Grok and all that? IIRC Elon has the biggest GPU compute cluster in the world right now, and is currently training the next major version of his "competing in the marketplace" product. It will be interesting to see how this blog post ages.
I'm not dismissing the rest of the post (and indeed I think they make a good case on Elon's hypocrisy!) but the above seems at best like a pretty massive blindspot which (if I were invested in OpenAI) would cause me some concern.