Each of the Court models under their Court of the Archon rule includes:
"In addition, if your army is Battle-forged, this model does not take up slots in a Detachment that includes any <KABAL> Archons."
In matched play you can only include them in a Detachment that includes an Archon (p114), so unless you are unbound then they can't take up elite slots. And if you are unbound then you wouldn't care whether they do or not...