Arch-Fiend
Explorer
Well, since there are those 5 sub-classes, it is not validated.
It is an interesting variant though, especially if considered as a broader re-imagining of the game in which all PCs have parity in terms of supernatural powers and resources.
if hitpoints are completely arbitrary for the dm to simply decide what they mean at any time, then that alone validates any interpretation of what hitpoints are. but furthermore if only 5 subclasses in the game are the classes that dont have some supernatural abilities to them then that further validates the idea that super durability can easly side into the build of the game as it is. this is what im saying.