Going from /etc/init.d/tmpfiles.dev which calls /lib64/rc/sh/tmpfiles.sh ... tmpfiles_dirs='/usr/lib/tmpfiles.d/ /etc/tmpfiles.d/ /run/tmpfiles.d/' Looking at /usr/lib/tmpfiles.d/: cyrus-sasl.conf fetchmail.conf lvm2.conf mdadm.conf mysql.conf postgresql-9.3.conf samba.conf Now looking at FHS: http://www.pathname.com/fhs/2.2/fhs-4.7.html Quote: "/usr/lib includes object files, libraries, and internal binaries that are not intended to be executed directly by users or shell scripts." Since these files are obviously configuration they must be moved to /etc.
Blame systemd for violating FHS. http://www.freedesktop.org/software/systemd/man/tmpfiles.d.html
Yes, they are configuration files, but they are not meant to be edited by admins. That is why they are in /usr/lib. This is similar to how udev rules work. packages install rules that are not meant to be edited in /lib/udev/rules.d.