> both outputs of Claude Mythos, their (still) unreleased advanced model

That sentence gives the impression that Mythos might be released in the future. That's clearly not going to happen - it's already "released" in as much as selected, trusted partners can access it, and the rest of us get it in the form of Fable - which is Mythos but with filters that downgrade you if you try to use it for anything even remotely related to cybersecurity or biology.

(The other day Fable 5 downgraded me to Opus after I asked it to explain the difference between tusks and teeth.)

Genuine question here, why would you ask Fable to explain the difference between tusks and teeth? That's a task that can probably be handled by Haiku.