The master stone has never been open to everyone, Saphir.
Of course 1350 was open to everyone for some-time when it was the master stone, but that was a long time ago wasn't it?
I suppose in some pathetic way you may still consider 1350 to be the master stone - perhaps that is the cause of your confusion.
Given the skill shown by the Mystics during the stone war I'm not surprised to hear that you are unable to understand simple agreements.
Written by my hand on the 28th of Mournsend, in the year 959.