I find Splane’s explanation fantastical. The only persons who could believe that the Biblical word “generation” means “overlapping generations” would be brain dead zombie JWs who will die rather than disagree with the WT.
There are two groups within this cult who refuse to think; there are the administrators of the religious racket whose existence depends on the mass of believers. They have gladly inherited their roles and job number one is to shore up their own rights to control the larger group. Their function is to make their religion credible and to retain the confidence of the followers. The second group who are duty bound not to think, are the true believers who are led by the GB. (Misled is probably a better word!)
A common thread within the JW org is the normal and unquestioning practice of belief in fantasies.
For example the stories about Biblical characters are dredged up in the Watchtower all the time as examples of faith. Who is there among JWs who would stop for a moment to consider whether these men and women were real? The WT gaily trots out names such as Noah, Adam and Eve, Abraham, Moses, Isaac and Jacob, etc, as if they lived! They are archetypes or mythical persons often borrowed from other cultures but given new Hebrew names -- they are all non-historical literary personages. Once a believer has swallowed the bait of Bible faith -- anything goes, anything is possible and anything can be believed.
Once in the JW mindset, it is not difficult to shut down critical thinking, living for paradise is the goal and that means, at least in the mind of the true believer, obedience to who they are taught to respect as “God’s anointed”.
Back on the theme of Biblical words, Jesus explained clearly and unambiguously how long a generation was: namely the lifetime of a group experiencing one event. Mark 8,38 - 9,1.
Yes, as the outcome (or lack of outcome!) of these words show, the "JW generation" is just a fantasy built on top of another Bible fantasy.