HP is going to be a system mechanic rather then an actual real world analogy. I tend to view the stamina system as more of a personal force field or aura protection for RWBY fans. But I think the smaller race having less HP makes sense. Now you can factor in stuff like density or thickness of skin but also the same size cut on a hafling means vastly different things for a Half Orc. A stab that does a few inches into a Half Orc is likely to do far less damage then it would to a halfling simply due to scale. Halfing smaller ergo stab is relatively deeper and far more likely to hit something vital assuming similar anatomy.
