See there ya go. No hard and fast rules.
I've never read that Hillbilly, but ya know what? It would make sense. The indian could peel off the bark off a sapling and do it like HHB, not touch the whitewood at all, or at most scrape off just a ring or two, if that much. We do know that the native always looked for the easiest and most efficient method to get his meat, and this would fit the description.
when you try a sap/heartwood BL be sure and let us know how it turns out.
~~Papa Matt