sam:rc: rc-service -U syncthing start
 * You are attempting to run an openrc service on a
 * system which openrc did not boot.
 * You may be inside a chroot or you may have used
 * another initialization system to boot this system.
 * In this situation, you will get unpredictable results!
 * If you really want to do this, issue the following command:
 * touch /run/user/1000/openrc/softlevel
 * ERROR: syncthing failed to start

and then if you look at /usr/libexec/rc/sh/openrc-run.sh:
verify_boot()
{
        if [ ! -e ${RC_SVCDIR}/softlevel ]; then
                eerror "You are attempting to run an openrc service on a"
                eerror "system which openrc did not boot."
                eerror "You may be inside a chroot or you may have used"
                eerror "another initialization system to boot this system."
                eerror "In this situation, you will get unpredictable results!"
                eerror
                eerror "If you really want to do this, issue the following command:"
                eerror "touch ${RC_SVCDIR}/softlevel"
                exit 1
        fi
        return 0
}
....
for _cmd in $extra_started_commands; do
        [ "$_cmd" = "$1" ] || continue
        if verify_boot && ! service_started; then
                eerror "$RC_SVCNAME: cannot '$1' as it has not been started"
                exit 1
        fi
done