Chris Siebenmann discusses when the OOM killer triggers: https://utcc.utoronto.ca/~cks/space/blog/linux/OOMKillerWhen
Chris disables systemd-oomd after it obliterates his X session with no explanation: https://utcc.utoronto.ca/~cks/space/blog/linux/SystemdOomdNo...
> > [...] If the configured limits are exceeded, systemd-oomd will select a cgroup to terminate, and send SIGKILL to all processes in it. [...]
> By having the user@.service template be enrolled in systemd-oomd, Fedora made the cgroup that systemd-oomd would select to be killed be all of your processes (across all of your sessions, if you have more than one). ...
Maybe *Fedora* has fixed or improved in the last 4 years. Or maybe they don't run Fedora.