It is likely that one spot of the "duke" postion is used to invite players outside borders early on to remove this.
Still it poses some issues. If player opens temporary treasury there, gets oases and deactivates the oases are still highly contested by surrounding kingdoms and may be lost any minute.
And if a player, as Qwr mentioned, becomes duke for a few seconds and then gets demoted to governor instantly he will simply have no oases.
Anyone constantly playing with 15 coppers and heavy gold usage will see that this update makes life much harder for them.
And it makes life better for Free to Play players. So I still stand by my arguments.