Re: 4.0 would be perceived as more different than 40
Or maybe they lacked the guts to treat versions as arbitrary, like Linus did when 2.6.x ended so made up a story.
One thing the both Ubuntu and Microsoft got right was the use of dates as version signifiers and IMHO this is what everyone with projects based upon constant, iterative changes should be doing. This way, documentation can be simplified by saying "X was introduced in November 2020" or "Y was removed in July 2021" rather than referencing meaningless version numbers.