Excellent - now you've explained what you mean by "Perfect Bayesian" it all makes sense! (Though I can't help thinking it would have saved time if you'd said this earlier.)

Still, I'm not keen on this redefinition of the word 'metaphysics', as though your philosophy of mathematics were 'obviously correct' 'received wisdom', when actually it's highly contentious.

Anyway, I think this is a successful attack on a kind of "Bayesian absolutism" which claims that beings who (explicitly or implicitly) assign consistent probabilities to all expressible events, and update their beliefs in the Bayesian manner, can actually exist. That may be a straw man, though.