Unfortunately, that is not set (just default commented), and that file is identical to the FC25 version. There doesn't seem to be any other reference to that parameter in the config directory either:
cpayne@k-2so:/tmp$ cat /etc/redhat-release
Fedora release 25 (Twenty Five)
cpayne@k-2so:/tmp$ grep -r KillUser systemd-fc26/logind.conf
#KillUserProcesses=no
cpayne@k-2so:/tmp$ grep KillUserProcesses /etc/systemd/logind.conf
#KillUserProcesses=no
cpayne@k-2so:/tmp$ diff /etc/systemd/logind.conf systemd-fc26/logind.conf
cpayne@k-2so:/tmp$ grep -r KillUser systemd-fc26/*
systemd-fc26/logind.conf:#KillUserProcesses=no
cpayne@k-2so:/tmp$
Anything else to check? Thanks for the help.