/etc/X11/prefdm chooses a display manager according to the desktop
preference in /etc/sysconfig/desktop
I need remote XDMCP features, and therefore I run xdm (because gdm doesn't
support indirects (etc.) as well as it should). In the present
configuration, I can't choose to run a Gnome desktop and have
/etc/X11/prefdm start xdm at the same time.
I think the display manager choice should be seperated from the desktop
This is a custom configuration issue. The choice of associating the window
manager that goes with the desktop that is chosen is what most users are
expecting by default. If you wish, you can modify /etc/sysconfig/desktop to be
"AnotherLevel" and then use switchdesk to change your individual preferences.