Maybe not. You stated "Every country will pursue it as far as it can, and given the multipolar world we are back in, and our recent record with treaties and commitments, I do not believe there will be global alignment on risk reduction" and that is true. While Anthropic may hold of releasing Mythos I don't think they will for long. As long as there is someone somewhere in the world that releases a competing model then Anthropic will be forced to release Mythos. This also assumes that its not a marketing tactic from Anthropic in the first place, build suspense before releasing it.

I would like to see more countries capable of producing frontier models. At the moment we have two in the world but many countries are building their own national models and AI infrastructure and may join the race.

Having a multipolar world may actually result in more freedom in gaining access to frontier models.