You can certainly put a directory wherever you like and put the code there. In fact, that's exactly what the author did, as he describes in the article.
What you can't do is just magically have that directory be the "home" directory of a user and have the $HOME environment variable always point to it. You might be able to set things up to do that in principle, but it might not be worth the trouble as compared to other solutions. In fact, that's pretty much the position the author takes in the article for his use case.
> the position the author takes is "i've never heard of `venv` so i'll do these other terrible 5 hacks instead".
No, it's "I don't need the full power of venv so I'll just put the code in a specific directory now that I've figured out how to tell pip to do that when it's not a user's home directory". Using pip install's "--target" option hardly qualifies as a "terrible hack". The designers put it there because there were valid use cases for it. Setting environment variables before running a program is hardly a "terrible hack" either; it's one of the most common uses for shell scripts.
> $HOME or not is a red herring
If all you meant by it is "put the code in any directory you like", then, as I said, that's exactly what the author did.
You can certainly put a directory wherever you like and put the code there. In fact, that's exactly what the author did, as he describes in the article.
What you can't do is just magically have that directory be the "home" directory of a user and have the $HOME environment variable always point to it. You might be able to set things up to do that in principle, but it might not be worth the trouble as compared to other solutions. In fact, that's pretty much the position the author takes in the article for his use case.