Hello,
excerpt from /etc/systemd/logind.conf:
[...]
# Entries in this file show the compile time defaults. Local configuration
# should be created by either modifying this file (or a copy of it placed in
# /etc/ if the original file is shipped in /usr/), or by creating "drop-ins" in
# the /etc/systemd/logind.conf.d/ directory. The latter is generally
# recommended. Defaults can be restored by simply deleting the main
# configuration file and all drop-ins located in /etc/.
#
# Use 'systemd-analyze cat-config systemd/logind.conf' to display the full
config.
#
# See logind.conf(5) for details.
[Login]
#NAutoVTs=6
#ReserveVT=6
#KillUserProcesses=no
#KillOnlyUsers=
#KillExcludeUsers=root
[...]
which suggest that by default (one may modify it by creating a custom
file in /etc/systemd/logind.conf.d/) systemd-logind.service dos not kill
user processes (root user included) and lets the killing of system
processes to systemd-halt.service
