How your /etc/systemd/journald.conf looks like ? Mine, on all my boards, everything is commented, so disabled ...
Even for myself, some RTFM is always good, we always have something to learn... Here are some reading : "man journald.conf" .
Yes, it is matter : simply to know what is logged in this files to figure out who is using it, maybe a specific appllication. I can't verify on my side, since none are created ...