> But a place like Las Vegas is literally a created city

What city isn't a "created city"? Think the answer is the same for any city.

That's not what the guy said though. He said you can't put LVP above radiant heat because it will be a vapour barrier AND severely limit heat radiation. That is categorically false, heat will radiate through a vapour barrier without issue, and that's why we need insulation.

I absolutely agree that a concrete slab which is heated with radiant, should have insulation + vapour barrier below and around it to limit heat loss in directions you don't want, but that isn't what the guy I was replying to was talking about.

A vapour barrier stops vapour, not heat. You can absolutely install some brands of LVP (f.ex Coretec) over a radiant heated slab without issue.

You can absolutely buy a variety of flooring that is radiant heated floor safe.

Coretec LVP can go over radiant heat (and is a floating floor), and I actually just bought some engineered hardwood flooring that is designed to be installed over radiant heat as a floating floor (gonna delivered today).