I think this is spot on. And is hard to understand while working for yourself and thinking your knowledge may become obsolete if you don't know the latest trending tech.
If your knowledge is becoming obsolete, then you weren't really, actually learning the concepts, you were just copy-pasting recipes.
You might have misinterpreted what I tried to say. I was talking about languages/frameworks, not the theory behind them. I don't think is feasible to go to a interview for a job that asks for node expertise saying you know the concepts behind node but you haven't used it yourself in a project.
I think it is reasonable, and I've actually gotten jobs that way.