Except it was. It wasn't regurgitating the exact answer it gave you, but it was using the collective knowledge of StackOverflow/other code to generate the solution.
Give your head a shake.
Fundamentally I only know about a language's functions/keywords/types/... because I've read them in some documentation or code snippet somewhere, but if I combine them in a new way to solve some previously-unseen task, I'd consider that to be creating something new.
Anything I've ever done at work could have been pieced together from StackOverflow. Anything you have ever done can most probably be pieced together from StackOverflow as well.
Also, I never said it was a "downside". I'm simply stating that the author is exaggerating what the LLM is doing. It isn't creating novel code.
I used LLMs all the time to spit out boilerplate when it makes sense.