There's a time and place for a full-stack developer like you mention, but I feel like there's an expectation that they should also be a hyperproductive 10X developer then.
I've seen and worked with people that have that ability, but in practice you see that they're going too fast and miss things like documentation, testing, or even basic architecture.
I mean yeah great that you could knock out some microservices, but they're undocumented nodejs services with a postgres database that communicate with each other using REST / JSON and there's nothing in the way of tracing or logging or status monitoring yet. Why not start with a monolith first in a sane language?
But by the time that question had come up, the guy already moved on to something better paying, lol.