AISI did also say that GPT-5.5, which has been public for months, scores basically the same as Mythos on their cybersec evaluation. But there wasn't as much media about about that for some reason.

https://www.aisi.gov.uk/blog/our-evaluation-of-openais-gpt-5...

AISI found the release version of mythos preview outperformed GPT-5.5 https://x.com/AISecurityInst/status/2054589763173126339