[JAlexoid]

There are massive differences between front-end and backend engineers.

Backend engineers deal a lot less with network instability, than frontend engineers. Frontend engineers have multiple ways of dealing with failure. And frontend engineers have a different ways of dealing with parallel and async tasks, than backend engineers.

It's not a massive challenge for a smart person to learn, but we shouldn't pretend that people don't try to apply their previous experiences to future tasks. Which is a cost, when hiring someone without specific domain experience.

[mbrodersen]

Nope not true. I routinely switch between working on Typescript/React web applications and hard core C++ servers, compilers and optimisers. Most of the skills you need are the same.