Create a mission in the editor.

Place a Blufor rifleman as the player, a Zeus GM module and link them (also make the rifleman the controller of Zeus).

In description.ext write this:
respawn = 3;
respawnDelay = 2;
respawnOnStart = 0;

Export as a multiplayer mission and load it up.

You will play as the rifleman. Change to Zeus, place a Blufor spawn module. Change back to the rifleman and kill yourself. You will have no spawn points.

Repeat the process, but this time add:
respawnTemplates[] = {"MenuPosition"};
to the description.ext.

This time, when you die, you will get the spawn point selector, although it has only one choice - the Zeus spawn point.

Somebody on Reddit thinks it's to do with this;

"There seems to be 2 types of respawn: respawn position and respawn marker. Zeus create respawn position and Base respawn uses respawn marker."