More on whether understanding requires knowledge

In the last post I suggested that understanding needn't be factive, and hence isn't a species of knowledge.  I also suspect that understanding needn't be doxastic (viz. doesn't require belief).  Take for instance a historian of science who understands phlogiston theory, but doesn't take it to be true.  There's a retort here: sure enough the historian of science doesn't believe phlogiston theory, but there is something she is required to believe about phlogiston theory in order to have understanding; i.e. that such and such is what people took phlogiston theory to be, that "phlogiston theory" denotes such and such propositions, or whatever.  Certainly, in most ordinary cases of understanding, beliefs of this sort will be involved, but these might only be a contingent feature of ordinary cases of understanding, not essential to understanding itself.  Imagine a whimsical wizard implants in a person S's mind a grasp of some such theory $\Gamma$.  This person, being epistemically cautious, whilst having a conceptual grasp of $\Gamma$, forms no beliefs about its origin, its truth, whether anyone else believes $\Gamma$, or whatever.  It seems coherent to imagine someone who understands $\Gamma$ without having any beliefs about it (other than trivial ones such as "I grasp $\Gamma$").