They rather shot themselves in the foot with the statement that "the canon was already settled by then, not by the decree of any council, but by the usage of Christian congregations throughout the ancient world.'
There is plenty of proof that many of the Churches/Congregations in the 1st Century used Books, and sections of Writings that are rejected by the Org for various reasons, none of them very Scholarly reasons. Revelation upon which they rely for their Armageddon nonsense was in dispute, and little used it seems in the early Christian Churches, and of course the dispute about the legitimacy of Revelation carried on at least until the time of Martin Luther.
The truth is the Org accepts the Protestant Canon, which was fixed when ?..... Exactly.
The big question is why do they accept these writings alone ? They have no genuine reason to do so, their arguments in support are as usual, fallacious.