Dog breeds developed to work in water generally have a high oil content in their coat so that water runs of the guard hairs and does not penetrate to the skin. (canismajor.com)
Depending on oil content of peanut butter, you may wish to add coconut oil to make it more fluid. (eatplaylovemore.com)
The only difference I've found is that the salt has more difficulty sticking to the popcorn with the lower oil content, giving it less of a flavor. (pastryaffair.com)