"Bayes oracle" was really just a term I invented right then, and it was a bad choice. I just meant that there is an optimal output symbol at each step, but that we can't necessarily write down a turing machine that actually generates it. This is not about halting-style uncomputability, rather it's about having to implement an algorithm as a tangible computation, and hence not being able to pause time while we make decisions.

If this sounds confused it's because I am!