This topic has come up several times. Yes, there are instances where the WTBTS directed destroying unbundled Watchtowers in JW libraries in favor of the bundled versions. This controversy has been the case since the Watchtower Library came out on CDROM, despite having the capacity to hold all articles going back a century, they intentionally did not put in anything referencing 1975 and the various books, Truth, Everlasting Life, Knowledge have been revised multiple times both in print, on CD and online. Many of the older books have since been completely removed online and were directed destroyed from JW personal libraries.
There was at some point someone who decoded the proprietary format the WTBTS made the CDs in, so you should be able to get the CDROM from year to year and compare them with some code to see all the changes that are made to the historical documents.
I know they did it for the “Evolution” book, because they were getting sued for misquoting a pre-eminent scholar (I think they did the same to atheist Richard Dawkins later on, making it seem like he is arguing for a god)
The 1989 Watchtower used the term "in our 20th century" in the magazine, but this was changed to "in our day" for the bound volume and subsequent CD library.
https://www.jehovahs-witness.com/topic/105270/question-blondie
https://www.jehovahs-witness.com/topic/101291/itemized-list-revisions-daniel-book
https://www.jehovahs-witness.com/topic/196792/blatant-misquote-origin-life-booklet