You know, because we knew this would be controversial we made sure it was both a compile-time option and a runtime option. Yes the upstream default of both defaults to on, but that's just upstream. We made it very easy and supported for downstream distros to switch between opt-out and opt-in of this option for their users. We have encouraged distributions to leave it on, but we were fully aware that for compatibility reasons this is something downstreams likely wanted to turn off, and most compat-minded distros did, as we expected.

Now I am used to taking blame for apparently everything that every went wrong on Linux, but you might as well blame your downstream distros for this as much you want to blame us upstream about this, as it's up to them to pick the right compile-time options matching their userbase and requirements in compatibility, and if they didn't do that to your liking, then maybe you should complain to them first.

(And yes, I still consider it a weakness of UNIX that "logout" doesn't really mean "logout", but just "maybe, please, if you'd be so kind, i'd like to exit, but not quite". I mean, that's not how you build a secure system. We fixed that really, fully knowing it would depart from UNIX tradition, but that's why we made it both compile-time and runtime configurable)

(Also, nobody has to "incorporate" systemd's library to avoid the automatic clean-up. In fact, there's no library we provide that could do that. What was requested though is to either run things as child of systemd --user or just register a separate PAM session, neither of which requires any systemd-specific library.)

Lennart