Like others have noted, it could be either one--I do know that the price cutoff is definitely a possibility; typically, the pumps cut off at $50 (varies, but that is the typical amount) when a CC is used. I have had this happen with two different trucks at more than a few gas stations.
But FWIW--yeah, on my '04 DXL, the pump seems to cut off a bit earlier than expected--i.e., I can typically pump another gallon or so after initial cut off...