The really odd thing is there wasn't a Governing Body until 1975!!!! But the choosing appointment of the FDS happened in 1919? Try pointing that out to your favorite JW.
They'll probably point you to the July 15, 2013 WT, p. 22, par. 10: "In recent decades, that slave has been closely identified with the Governing Body of Jehovah's Witnesses." There's an admission in there, that the 'slave' was not always identified with the Governing Body, only "in recent decades". Which means it was first Rutherford, then Knorr, then Franz, then the Governing Body. There always was a board of directors that filled the GB role, but the President had the final authority, until the Governing Body wrested that control from Franz.
But it's not really going to be relevant to a JW, since 'the truth' was still being taught and preached all over the earth because of this organization. Where's your organization, and why aren't you knocking on doors? See, this is the problem with apostates, they keep picking at these little things, but they produce no beneficial fruit at all. And that'll be the end of that discussion.
--sd-7