Hmm, a matter of definition........what could be more cognitive dissonant than believing in something you know is not true?
In case it's not dissanance they have to "suffer" from some kind of dissociative disorder or multi personality disorder.
So, OK...maybe their "cult personae" are believers , but their natural or true personae realizethat it's wrong. Maybe then cognitive dissonance is somewhat related to dissociative syndroms...e g the different personae cult researchers like Steven Hassan is talking obout!
One religion psychologist professor here in Sweden (Owe Wikström) uses the expresion "two floor people" about the cognitive dissonant. At he top floor/upper level they are rational and well funktioning, but in the bottom floor/basement you have a lot of irrational thoughts and fears that cripples them.
In some weay this is related to the splitting in different personae (Hassan) , which I see as some kind of dissociative disorder.