systemctl start vncservr

I was trying to configure vncserver as a "root" then got below status which really made me thinking that root can not be accessed remotely thru vnc viewer as kind of security on RHEL7 . Then decided to create some users only for this purpose and everything went smoothly but still had some curiosity to figure out what's the root cause behind that , I killed all the PID which were opened before for user "root" , deleted the .vnc directory from root's home directory and tried to reload the copied configuration from /lib/systemd/system/vncserver@.service many times but whenever start the service getting same message , by the way selinux and firewalld are already disabled in my system.

then suddenly something weird happened !!!
I successfully managed to land on root GUI from vncviewer using [myserver's IP:3 ] in spite of getting this message from systemd which let anyone believes that something somewhere was configured wrong then the service is not running !!!!

Is this a "' bug "' on RHEL or what ?
I'm really confused !!!

[root@myserver ~]# systemctl status vncserver@:3
\u25cf vncserver@:3.service - Remote desktop service (VNC)
Loaded: loaded (/etc/systemd/system/vncserver@:3.service; enabled; vendor preset: disabled)
Active: failed (Result: resources) since Wed 2019-02-20 20:21:29 +03; 16min ago
Process: 3362 ExecStart=/usr/sbin/runuser -l root -c /usr/bin/vncserver %i (code=exited, status=0/SUCCESS)
Process: 3299 ExecStartPre=/bin/sh -c /usr/bin/vncserver -kill %i > /dev/null 2>&1 || : (code=exited, status=0/SUCCESS)

Feb 20 20:21:19 myserver systemd[1]: Starting Remote desktop service (VNC)...
Feb 20 20:21:29 myserver systemd[1]: PID file /home/root/.vnc/myserver:3.pid ...t.
Feb 20 20:21:29 myserver systemd[1]: Failed to start Remote desktop service ...).
Feb 20 20:21:29 myserver systemd[1]: Unit vncserver@:3.service entered faile...e.
Feb 20 20:21:29 myserver systemd[1]: vncserver@:3.service failed.
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