I'm not sure whether poster Richard Oliver is a blatant shill for the Watchtower, a shameless apologist for them, or just the king of rationalization.
All the things he mentioned are actually plausible, but we're not talking about variations between different language versions of a particular magazine issue. I think we all know the real reason online versions and reprints, especially those of older literature, sometimes differ dramatically from the original printed versions. Changes are made from time to time to alter or remove embarrassing or blatantly false statements.
Just one example: In the January 1, 1989 Watchtower magazine, on page 12, it says, "The apostle Paul was spearheading the Christian missionary activity. He was also laying a foundation for a work that would be completed in our 20th century." When the bound volumes of the 1989 Watchtower came out, the text of the January 1 article had been changed so that it now stated the work would be completed "in our day" instead of "in our 20th century." The only possible explanation for this change is that they wanted it to appear that they had never predicted that it would be completed in the 20th century.
I believe this policy of covering up earlier statements that are now embarrassing is the main reason the Society's online library only goes back a few years, to about 2000 or so. All that old light must be way too much trouble to edit out and rewrite, so the next best thing is to do away with the evidence itself. That's the main reason congregations were ordered to destroy certain older publications and are definitely NOT encouraged to have a collection of historical Watchtower literature in their Kingdom Hall libraries. I have heard of some congregations dispersing or destroying their valuable collections of early literature solely to keep it from "falling into apostate hands." Some of those older books are now so rare they command hundreds of dollars on eBay and such.
If this sounds familiar, just read 1984 by George Orwell. The Orwellian World of Jehovah's Witnesses, by Heather and Gary Botting, draws many more parallels and is an eye opening read. It was originally published in 1984 (coincidence?), but much of what it says is even more true today than it was then. Both books are still available on Amazon and the like, and you can often find copies on eBay as well.