So many comments here missing the big picture, and just gleefully pointing out that Anthropic got what they deserved, or that this is the natural culmination of some kind of marketing stunt. The real story here is that this may be the beginning of governments restricting the availability of strong LLMs to the public, to you. Fable was the strongest model on the market, and the US government has told you you can't use…
The "Mythos capabilities" is a pretty arbitrary threshold. It could have happened any point before or after. China treats this technology in very different ways. And China's economy and foreign policies are very different, in such export-based economy export controls make much no sense. Unless something changes drastically in the global relations. I expect the opposite to happen, if the US leave a void globally, china will be even more incentivised to fill it.
This been said, it is likely that big models are soon no longer "open sourced" (qwen has already started), but because the chinese companies will prefer to sell access themselves, not because of government intervention.
In any case, what happens now is a huge thing, and not sure we grasp its consequences yet. It is definitely beyond any ai safety marketing stunt. Even if this is rolled back at some point, after "guarantees" are established, it has already moved things to change drastically.