First, Anthropic was founded by people who we know were worried about AI safety and signs point to that still being the case. It's really cynical to say it was all an exaggeration for marketing.
Second, this isn't Moller promising a fantastic working flying car next year. The model did what Anthropic said it could do.
I realise that ruling out "they bought Anthropic's scaremongering" brings up the question of why the government would block Mythos/Fable, but not the roughly-as-capable and less restricted GPT5.5. However we do know for a fact that they dislike Anthropic more than OpenAI right now.