Unfortunately, composer cannot load repositories this way (for a good reason)...

Unfortunately, composer cannot load repositories this way (for a good reason). So, the patch cannot work even if merged because composer will never read this repositories entry. The repository has to be added to the root composer.json (the main composer.json for the site). This was covered in the documentation changes introduced in #2918901: Fix documentation for composer library setup.

@cantrellnm, I know what you mean and I had submitted a PR to the package but not yet merged. Hopefully, the maintainers review it soon and merge it which will make the process easier.