Nothing to do with the devs, it's that Linux has, as you say, a distributed cabal of individuals while most things on Github have a nondistributed set of size 1. The reason why it's hub-and-spokes is that that's all you can do with only one or two people, or even half a dozen apparently when only one or two are doing all the work. If the <x> maintainer doesn't accept your PR it is a big deal because there's no-one else there to accept it. Even worse is when you've got the opposite, one or two devs spread across half a dozen projects (HACS springs to mind) where they never respond to anything on most of the projects because there's essentially 1/10th of a developer on each one even if the apparent maintainer list is several people.