This isn't entirely true.

Knowing how react works (or doesn't work) helps a designer design a valid experience that can actually be implemented by the developers. Ok maybe they don't need to know React, but surely they need to know what a browser can and can't do.

A react developer (web developer) needs to know how tcp/ip networking works to avoid spending hours of debuging communication problems with XYZ service.

And so on.

Surely people can go about doing their jobs without necesserily knowing how the adjecent stacks work, but they would be way better professionals of they did. I would agree more with your argument if you restricted the distance of irrelevant tech-stack to let's say 3 levels. Eg, the web developer truly won't do any better if they knew more about kernels.

I like thinking of it like the Olympic rings. The blue ring(all the way to the left) doesn't need to know anything about the red ring(all the way to the right), but should absolutely know the yellow ring(second ring from the left), and possibly bits of the black ring(middle ring). The leakier the abstraction, the more you need to reach.

But it's mostly true, and that's what matters.

Nobody's trying to build a super rigid structure around the division of labor, they're just trying to create a general set of guidelines that will help answer questions quickly.

>The kernel developer doesn't need to know how a CPU works.

>The CPU engineer doesn't need to know how silicon metallurgy works.

You're sure about this?

I'd argue that each of these should have a good understanding of the layer below (and maybe above) them.

OSI model of Human Resource Management?