It's not really doing that though. Nc+head/cut/grep are and youtube-dl is grabbing the data. Bash in this case is just orchestrating the order of communication between the tools doing the actual work, as a normal Bash script.
The post is about doing all of this in pure bash builtins like /dev/tcp and bash functions. Not about gluing together tools which do the work.
Yeah, it's a nifty little tool. On the other hand when a really interesting post on pure bash exposition comes up the comments section turns to talking about plain bash scripts they've made or know of instead. There are several normal scripts replied in this post and a few others via links, more than actual conversation around what the post is actually about (so far). That's all I was commenting on, not the value of the tool. It's a hill :).
Even the post isn't using /dev/tcp, but compiled a C file into bash "loadable builtin" (which is something I learned today). It still feels kind of cheating to me tbh.. But cool enough!
The post is about doing all of this in pure bash builtins like /dev/tcp and bash functions. Not about gluing together tools which do the work.