Are there any publicly verifiable sources that Mythos is that much more intelligent than Opus, so to be considered much more dangerous (as it is presented in the public discourse by Anthropic)
It doesn't have to be _much more intelligent_ than Opus to be a risk. It doesn't even need to be _more intelligent_. It just needs to be _better at finding security problems_. Which could happen from just minor improvements in training data, or the harness, etc. Even a small improvement could shift it from finding very few new security holes, to reliably finding many at scale.
Yeah, I think a lot of the disconnect here is that people think of "model intelligence" as some sort of IQ score, rather than a combination of scores that measure abilities at a large variety of domains.