Yes, this kind of "naive coding technique" occasionally pops up, and I think it's a good discussion topic, because its mere existence demonstrates that you can get extremely far in terms of delivering features with a minimal amount of abstraction: "sometimes all you need is a function."

Further, that the code probably would not really be hideously miserable for a more experienced coder to refactor(it's just very duplicated) shows that copy-paste is reasonable for deferring some kinds of architectural decisions. It's not what you would bias towards if you have a whole team pounding away at the same file and rapidly evolving it, but as a solo practitioner who wants to get the feature out and put it away for the day, this style is convenient for letting the code as a whole develop some maturity and functionality before it gets refactored with abstraction.

Give refactoring this code a go! Its sublimely fun!!!

https://intuitiveexplanations.com/assets/Resume.pdf - author's resume is pretty impressive. Glad to see he's doing well.

But isn't this the beauty of programming to begin with. Barring certain things like medical devices, cars, etc., where it has to be very orthodox, for stuff like Web back/frontends, and even gaming, this is how people learn, I guess. Sure, that code could be re-factored for speed, cleaner in appearance, etc.

Reminds me of the video driver (forget card) some Linux developers wrote that was ~30k lines of code. OpenBSD wanted to use it because the HW manufacturer wouldn't release the specs, but because the Linux code was GPL, the OpenBSD guys re-wrote it from scratch in less than 1/4 of the code.