We already discussed it somewhere else.
It doesn’t make sense that a UI modify the behavior of the other one.
Such cosmetic issue is present just because you have installed both the UI and you’re accessing both.
If you have already configured the machine using Cockpit, you can just press “next next next” on the nethgui wizard. If you want to totally skip it, just execute:
config setprop httpd-admin ForcedLoginModule ''