If it's main function is to affect the Spirits then it belongs here.
Wan, Aang, Mako, Biolin, Korra were all healed by the spirit water. As you know (hopefully), they weren't spirits at all, so this water isn't applied to only, or even not, to the spirits.
Now, I just started to realize what you might have meant by your statement, since it is probably used to heal the spirit within them, but if that was the case, aang would have still died after being resurrected, because I believe bad conditions from the physical body wouldn't be capable to recover by the sprit that got healed within him. It just sounds silly to me. Spirit can not influence for the person to stay alive if she/he has fatal wounds/injuries or the lost of something that supports them leaving, such as the person without a heart or pierced in, from what I can theorize.
Another thing, what I got from the wiki, Wan got healed from his injuries, which I can imagine it is referred to his physical injuries, by the spirit water. Again, for the same reason, I do not think that healed spirit can heal a physical one, neither that the spirit can get harmed by physical means (in Aang's case too) and of course it wouldn't need healing if it is already fine/healthy. All of it just sound silly to me for that process to exist.
I don't know any evidence that proves my points true, but if you do find those that prove my speculation wrong then I would disregard my opinion and would stick to those valid facts.