It is instructive to read what the Society has said in the past about overlapping generations.
In the September 1, 1952 Watchtower, a QFR article posed the question: "Your publications point out that the battle of Armageddon will come in this generation, and that this generation began A.D. 1914. Scripturally, how long is a generation?" The response said in part:
*** w52 9/1 p. 542 Questions From Readers ***
Three or even four generations may be living at the same time, their lives overlapping. (Ps. 78:4; 145:4)
Today, the Society would say that all four generations are really one generation, as they overlap together. In 1974, the Society again assumed that generations that overlap are, duh, separate generations:
*** w74 1/15 p. 43 How One Language Will Bring Unity to Mankind ***
There may well have been little change in Moses’ language from the original language spoken by Adam. Why? Because men then enjoyed very long life-spans, their lives often overlapping into five or six generations. Therefore, the language could have been passed down through only five human links between Adam and Moses, namely, Methuselah, Shem, Isaac, Levi, Amram. (Gen. 5:3-32; 11:10-32; 21:5; 25:26; 29:34; Ex. 6:16, 18, 20)
So here again separate generations may overlap with each other and still be considered distinct generations. In 2001, with reference to the growth of Australia as a country, the Society wrote:
*** g01 2/8 p. 22 Bound for Botany Bay ***
The pace of change continued to accelerate from those early days, and within just three overlapping generations, the “fine and flourishing colony” grew into a multicultural nation.
Because the three generations have overlapped, the Society today could just as well say that these are three groups comprising one generation, and that the generation of the Botany Bay colonists has by no means passed away. And similarly, they published in 2004:
*** w04 1/15 p. 5 Promises That You Can Trust ***
The Israelites were well received in Egypt in the days of Jacob’s son Joseph. The Egyptians later subjected them to brutal slave labor, but true to God’s promise, within a period of four overlapping generations from the time they entered Egypt, these descendants of Abraham were liberated from Egyptian bondage.
Again, the Society recognizes that generations may overlap without having the overlap render them as somehow comprising a single generation.
The Society's own literature shows how much the new "understanding" is contrary to normal English usage, not to mention basic logic.