I am not sure but since they seem to live forever they seem undead, regardless the point is immersion is almost always only limited to preference and imagination.
True, they do look like zombies and to be honest the first time I bumped into them in Fallout 1 I was pretty much, zombies run away, that was quite early in the game though, later on it was zombies, damn they are annoying.
And a bit after that it was they are what? Radiation mutated humans, seriously? And, they can talk? Really?
In Fallout 4 its pretty much the same for me early on its where did I put the shotgun, later on its where the hell has it gone after its jumped and passed through me, and is now stood directly behind me, which is even odder if you are wearing power armour, its pretty much how the hell did they pass through me, they are not to either side as if the hit and slid of to one side of the armour they are directly behind you, ghostly or what. And the damn annoying is still on the tip of my tongue when running into them. Easy to kill but still damn annoying, not quite as annoying as the flying bugs, and teleporting rad scropions, I know they are supposed to burrow under ground but that quickly?