When I and Tom came up with that, I don’t think we meant “belief” to be imbued with the usual philosophical connotations. Rather, we intended it to mean something like “action-guiding, introspectively accessible representation of a state of affairs existing independently of whether it is queried”.
When people ask me what I think about the world, I can often come up with lots of intelligent sounding answers—but it is unfortunately more rare that my actual actions, plans and normative evaluations are somehow suitably hooked up to, and crucially depend upon, those answers.
[Note: I double-checked with the moderators before posting this to ensure it was not too “marketingy”.]