I think that crossbreeding will be part of the "scale" in the "scale and sale". They crossbred Monster Silk silkworms as announced in the May 31, 2011 PR with commercial silkworms in order to have silkworms that are larger and will produce more silk. It makes sense that they would need to do the same thing with the Dragon Silk silkworms.
Though, i suppose, it is possible that they simply started with commercial silkworms when creating Dragon Silk, so if that were the case, it may not be necessary.