Genetically speaking, there's no reason why leucistics shouldn't have yellow spots. They still possess xanthophores. I've had a few that have had faint yellow splotches.
Spotting in leucistics is just a matter of how late the migration of color cells off the neural crest is turned off. In pure white animals, it happens very early in development and no color cells migrate from the neural crest. In heavily spotted animals, the genes are active (or inactive?) for slightly longer, allowing more color cells to migrate.
When you breed together two animals that are more predisposed to heavy spotting, it only stands to reason that their offspring would also be heavily spotted.