“Roughly, it takes 2x more time to write a patch if you are unfamiliar with the project, but it takes 10x more time to figure out where you should change the code.”
New contributors don’t get stuck on the code. They get stuck finding it. One short file that maps the modules fixes that, and it only covers what rarely changes, so it doesn’t rot. Maintainers ask for contributions and then hide the map in their own heads.