I believe that's nonsense. Out of all the software being packaged in all the distros out there, I would say only a very small amount is actually being packaged by people who are also upstream developers, there are LOTS of distros and LOTS and LOTS of packages out there.
>In the cases of Debian, Ubuntu, and Arch, for examples, the distribution's listed maintainers are also systemd developers.
systemd is a quite large project, some 250+ different committers, and from what I've read, neither Debian, Ubuntu or Arch will use the new default of shutting down user processes upon logout, despite them having upstream systemd developers responsible for the distro packaging.
> I believe that's nonsense.
You can believe that if you like, but yours isn't a belief in any way founded in fact. Tomasz Torcz's 2014 lists of the top systemd developers includes the Debian, Ubuntu, and Arch maintainers.
This is a dichotomy that does not exist in practice. It's the same people "upstream" as "downstream". In the cases of Debian, Ubuntu, and Arch, for examples, the distribution's listed maintainers are also systemd developers.
Not that one should take this as singular to systemd. The idea that there's some form of Chinese wall between a package's own developers and its maintainers at the various distributions is not reality in a number of places. Take mediawiki, for example. The person seeking to package it up and be its maintainer for Debian in 2016 is a Wikimedia Foundation software engineer.
* http://unix.stackexchange.com/questions/287761/
* https://wikimediafoundation.org/wiki/User:Legoktm_(WMF)