I associate the term "guardian" with .... "guardian angel" ...'messenger" and that remindes of
1919: The seven angels, or "messengers", of Revelation chapters 1 and 2 are identified "for the first time in the history of the church" as St Paul, St John, Arius,Peter Waldo, John Wycliffe, Martin Luther and Charles Taze Russell. "The Table of the Great King,", The Watchtower, April 1, 1919, as cited by James Penton, Apocalypse Delayed, pg 181
Watch Tower literature has suggested such enlightenment results from the application of reason and study, the guidance of holy spirit, and direction from Jesus Christ and angels. Rutherford spoke of spiritual "lightning flashes in the temple", the Society claims its doctrine of the "great crowd" and "other sheep" were "revealed" to "God’s earthly servants" in 1935, and Witness literature has also described sudden changes in doctrines as "flashes of light" given by God through his holy spirit. A 1930 publication claimed God used "invisible deputies" and "invisible angels" to pass his "messages" to The Watchtower, although The Watchtower told Witnesses it was not necessary for them to understand how this took place. A 1973 policy change to disfellowship tobacco users was explained as a decision that "Jehovah has brought to the attention of his 'holy' people".[26#
Thanks go to: https://en.wikipedia.org/wiki/Development_of_Jehovah%27s_Witnesses_doctrine
Perhaps the Governing body thinks that not St. Paul, St. John, Arius , Peter Waldo, John Wicliffe, Luther, Russel, but that the real messenger are those Governing Body member that saw "the generation" or 1914/1919, who knows?
It could be further that the Governing body members = Watchtower Directors of 1919 are the real messengers,
or it could be that 7 succeeding Watchttower directors: Conley, Russel, Rutherford, Knorr, Franz, Henschel, Adams are the messengers This would not include the current GB members though, who would be only agents of Adams.