No, it's not possible. They both eat. Suppliers are usually in the business of reselling them, not raising them. Your supplier doesn't know what they are talking about. They are often sold and resold in a dormant (starving) state. They basically starve to death (unless they are fed to a reptile first!
)
Wax worms are typically fed a diet of honey/glycerine/and some type of dry flaked baby food or grain. There are many different recipes that work, some even use graham crackers or dog food. I used to raise them using baby cereal, but it is a real pain. (compared to other feeders like crickets and silkworms)
Butter worms come (I understand) from a nodule on a plant that is then broken open to extract the worm. The plant is very similar to "tumble weeds" I am told. I don't think you can get anything comparable in this country to feed them, and I understand they are all imported, and never bred in this country.
Rodney