Set was an involuntary ally of the Master but an ally he was, hence why they had troops stationed inside the place.
A bunch of horrifying deformed mutants living in the sewers in an indestructible bunker is a bit different as a point.
At least this Vault is hidden, mostly, despite the giant Vault-Tec symbol in front of it.
Even without the Vault door it's unlikely. To adjust the comparison, it would be as if there were a hiidden cave of Lenape troglodytes underneath Yonkers. Yes, that would still probably be found.
My biggest question with the retcon of its location being now in the Boneyard (or at least Shady Sands being in Los Angeles County--maybe the Valley), is whether or not its meant to be the same Shady Sands location as the original games or if the community moved ala Rome over a hundred years.
The way the chalk board is written makes it pretty obvious that this is supposed to be the same Shady Sands.
It's not an arbitrary bar, because if there's radioresistant human beings walking around and producing offspring who are also radioresistant, then the wasteland isn't really a threat anymore. The survivalistic tension of the post-apocalypse gets halved and all you're left with is killer critters. There also wouldn't be any hidden ruins full of prewar goodies left because radioresistant humans could clean them out no problem. No need for expensive and hard to acquire drugs or PPE.
I agree that radioresistant humans could be
messy but it's not
setting-breaking. If proper controls are taken (IE, figuring out a reason why they're isolated or not overtaking the world), such a thing could be fine.
I'd also note that Bethesda has already done this in a much more egregious manner with the Children of Atom, who as of Fallout 4 have magical radiation resistance powers. At least the Vault 4 Dwellers (who are not even established explicitly as radioresistant) have some reason to be silo'd off.
And again - radio-
resistance is not radio-
immunity. Unless you have lead skin or a magical quad-helix DNA strand, radiation is going to have some effect on you. Degree of resistance varies based on mechanism.
I know you keep saying they may not be radioresistant, but we can't assume anything the show neither shows or tells us. If Vault 4 natives are directly descended from the gulpers then it's logical to conclude they're all radioresistant from gulper DNA. The problems and caveats you're thinking of should have been covered in the show itself, instead of contriving everything to set up a 2 parter joke with a literal punchline in the form of Maximus going on a rampage.
Given that phenotypically they bear almost no resemblance to Gulpers, who themselves aren't even explicitly established as being radioresistant (it is rather a first-order inference which I'm happy to accept as fact), than it's actually not so facile to assume that they would share that particular trait. And while the show
should have addressed this given the show
did establish this as the purpose of the fault, I'm happier to chalk it up to "bad writing" and "lack of vision" etc. than I am "fundamental setting break." That's just a step too far for me, to level a criticism like that on the basis of 2nd or 3rd order inferrence.