I feel like I've seen 2-3 articles alone in the last month that has rediscovered head-of-line blocking and UDP. I'd say 1/10 engineers I talk to even know what cache aware datastructures are.
The thing that separates someone who can just string together whatever they find on npm to people who build real systems is this deep understanding. You're not going to need this for your standard LoB apps. However if you're in the business of building software you're definitely going to want people like this.
Trying to find the TCP stack engineer to build your app is like hiring a petrochemical engineer to do oil changes. If your pockets are as deep as Google's, yes, you can do that, but it's by no means necessary.
Whatever this thing... this... stringing together a 100 random github projects to get a webpage that kinda of works about 80% of the time is called -- please let's agree not to call it "software engineering".
And that, ladies and gentlemen, is how we ended up with npm.
If you're interviewing for the rare 1% case where the job will actually require you to tinker with a TCP stack, then by all means ask about those details. For 99% of programming jobs today, it's irrelevant trivia used as nothing more than an ego measuring device.