To your first point, while the post is based on the assumptions that anthropic isn’t lying/exaggerating about Mythos, I still think you can take it at least as Anthropic signaling what they intend to do with a model with potent capabilities. As such I think you’d arrive at the same conclusion.
To your second point, the “Since the release of ChatGPT” is a nontrivial part of the statement, I do agree that it took time for models to be open to the general public but I don’t think the guarding was that severe. For example, I got access (completely random guy) to some OpenAI early research previews, and that was still before the release of ChatGPT. I don’t think its a coincidence AI companies started eagerly asking you to use their models (give them more training data) at around the same time they realized how much more training data they’d need.
One argument is that if public sentiment towards AI turns negative to the extreme, datacenter security costs may increase substantially. Building an orbital datacenter is one way of making it highly secure against the masses without worrying about obscuring the location.