I should know better, but I'm researching some stuff on the GB so I pulled out my old Aid book. Interestingly, there is no entry for "governing body" so I read the one on the Faithful and Discreet Slave. They say that commentators frequently say this is a generic sort of exhortation to any who hold a position of responsibility. They say that this can't be right because "one person" can't be placed over "all" of the master's belongings.
They then go on to talk about the fulfillment in the 144,000 and say "thus the entire Christian congregation was to serve in a united stewardship, dispensing such truths."
I don't know how I used to think this stuff made sense. Does the new book say much the same thing? I left before it came out.