There is good reason to be inclusive here.  At any given time, nearly all a person's beliefs are dispositional.  A good epistemological theory will then have to say something about the epistemic status of these beliefs.  So our definition of memory belief should not be limited to the exceedingly small class of occurrent memory beliefs.  Perhaps the epistemologist will need to have something special to say about occurrent memory beliefs, but our main topic will be more general than that.