I have zero evidence. But anecdotally (and working with Claude every day) I see wild swings in Opus/Fables abilities day to day. It really does feel like they are twiddling knobs behind the scenes and hoping no one notices.

They are actually doing it, it's the best business method you can do. Who says it's not, shut the fuck up you idiot, anthropic implemented a secret safeguard without announcement, of course they can tweak it