I'm saying that if they seem to have such a vulnerability, it was their choice to impose it upon themselves. And though I suppose it's theoretically possible for a person to make themselves vulnerable, I think in this case (choosing to step into the set of limitations that comprises "being human" for a while) it's more like existential roleplaying than actually "becoming" human. So they were infinite, having no such vulnerabilities, no "body" or "mortal needs" like food and such, no weakness that allows them to "suffer injury" or "get infected" or anything like that. And then they decided to pretend to be something much smaller and weaker. But they aren't literally human, just "playing human" for as long as they please.