I think we should change the Hardcore trait’s name to something else, “hardcore” here refer to the fact that the human player is playing in hardcore mode (aka super-hard mode) and while in the game world the character with this trait will have a hard time too, it’s different because one is playing a hard game and other is struggling for survival with a severe disadvantage. I suggest a more “in universe” name, something that reflect the character - not the player.
It’s a big stretch, but what about renaming it to “Just A Kid”? It’s a lot easier to justify frailty if we assume the survivor is only the size of a child themselves, though I’m all too aware of the other benefits/drawbacks that should also entail (higher recoil with guns, no access to big two-handed weapons, difficulty reaching things on counters, more hiding places, it just goes on). But hey, it’s also a vague reference to a notoriously difficult game, so that’s a plus I suppose.