The reason why I bring up the "seven churches" theory is because the modern JWs have no good answer when asked for links with previous generations. The messengers, if such they were, were not the FDS, but the current official definition of the FDS is that it is the composite Christian congregation of anointed ones who feed each other along with (in modern times) the "other sheep." Of course, we all know that the FDS is just a front used to prop up the authority of Brooklyn, and it has been discussed many times in this forum that it has nothing to do with the average JW who may claim to be anointed. That being the case, the theory of the "messengers" at least pointed to historical personages who were thought to have had the truth in their own time.
It's true, of course, that people such as the Waldenses would not identify themselves with JWs today. As far as Luther is concerned, the claim has been made that people who practiced the truth which was available in their own generation were God's servants at that time. They were living before the harvest. But now the light has supposedly gotten brighter, and today one must be in association with God's visible organization. This is the claim that is made.
I believe there was once a quote given in this forum wherein the Society attempted to leave its readers with the impression that there was a faithful slave throughout the centuries that has been feeding the domestics in the same way that the Society claims to do today. That is nonsense. But at least we can realize that these questions have various facets, and the Society does not always express itself consistently in its own bests interests.