It's not clear who you are responding to but you certainly seem angry.

Extracting code from one Python file to another in the same project, as in the example in the article, is in no way "optimization", nor does it have "expensive overhead".

When writing Python, you want to avoid both extremely large source code files and lots of tiny files. It is natural to split off individual classes or functions if they get bigger than a certain size, and it does not come with "expensive overhead".

Working in huge corporate environments for 40 years is not the gold standard of code. I've seen a lot of that code and a considerable quantity of it is pathologically badly written. Of all of these places, only Google had a mostly-excellent codebase. While I never worked there, I remember one time when Yahoo was unable to push any changes for almost a year because of technical gridlock.