I had thought it said something about token usage, but I just clicked on "Switched to Opus 4.8 - Why?" and it says:

> Fable 5 has safety measures that flag messages on most cybersecurity or biology topics. They may flag safe, normal content as well. These measures let us bring you Mythos-level capability in other areas sooner, and we're working to refine them. Send feedback or learn more.

Perhaps Mythos realizes the true danger in studying Chinese Archaeoastronomy that we mere mortals fail to recognize!