No, they didn't...
...they just conceded to use the phrase "many thousands of years".
And they had to wait until Freddy Franz kicked the bucket just to do that much.
It has always been axiomatic that since the 7th Creative day is thousands of years long (according to wt) wt also always concluded and taught that all days of creation are of equal lengths (7000 each). The Insight book, published in 1988, prior to the death of FF, says so, in fact that is what 1975 was about. What the insight book does not say is that the days are of equal lengths and the wording allows for varying lengths. However, it is in print or was in print that "yom" was or could have been millions of years old and of varying lengths. The WT are not scientists and have not taken the scientific measurements or estimates that show how old is the earth or the universe so of course they are not in the business of teaching science but regardless of how you word or describe what teaching means, the wt printed that the Creative days could have been or were millions of years old of varying lengths. It is also in print that the earth is billions of years old. One article that comes to mind talks about how looking into the sky is looking into the past because it took the light of stars millions of years to reach the earth. Who knows with certainty how old is the earth, not even science but science bases their conclusions on evidence, wt and everybody else accepts verifiable evidence.
You mean the absolute reams of evidence compiled by over a century of painstaking research by dedicated researchers in virtually every field of the natural sciences?How insightful and forward-thinking of them
WT is not in the science field, it is in the field of understanding the Bible; (verifiable) science shed's light on Bible interpretation not (speculative) science.