like just about everything in the snake genetics world, statistics is how we determine what is "fact." Chances of multiple breeders screwing up and selling double hets for the price of a single het, then selling those animals to other breeders who all produce similar results.... I'd say the chances are pretty low.
It would be interesting if it turned out to be a combo, but judging by all the other morphs that are allelic, i think its a safe bet to assume they are also.