I believe that the Watchtower Society's publications have given JWs a "mixed" message about this teaching over the past few decades. Officially, you would find that the teaching (prior to the new light in 2013) was that the Faithful & Discreet Slave (FDS) = any of Christ's brothers while still in the flesh over the past twenty centuries. And what is the FDS supposed to be doing? Giving out food in due season. The whole slave performs this, not just select members (at least according to Jesus parable).
We have all likely heard stories that some "Anointed" brother or sister would send in to Bethel what they believe is a clearer understanding of certain Scriptures, etc. But are these suggestions given consideration? That's where the mixed message comes in. Because the Society has acknowledged in its publications that not all who were part of the Slave, dispensed spiritual food. Dispensing spiritual food was up to the Watchtower Society representatives at Bethel, which effectively = President and other officials and then a bit later these members became more formally known as the Governing Body.
So I would say Rufus, you are correct when you write: "Can anyone tell me WHO in recent decades has closely identified that slave with the GB? I know it wasn't the GB who did so!" Officially they did not state that the FDS = the Governing Body, but woven into their messages through the publications was a mixed message --- and this is what groups of and individual JWs picked up on --- is the idea that the FDS was really only associated with the higher ups... the Governing Body.
As for me, when I was a JW (1970 - 1984), I would have stated the official doctrine at the time. FDS = all the remaining members of Christ's Body on earth. But if I was asked if ALL the FDS dispensed spiritual food, I would likely have responded, no... that action is performed by the Watchtower Society / Governing Body alone. Again, I would be acknowledging that effectively, only the Governing Body dispensed food. So it would not be too much of a leap for JWs to just accept that the Governing Body alone is the FDS.
ExpandedMind