That is just a fairy tale. Marketing decides the name of the release, and marketing wanted to indicate a clean break. Microsoft never had a marketing idea all on its own, so it did what Apple did: it released Windows X, just like Apple had done with Mac OS X. On top of that, the numbering jump was also a way to indicate this was the last version of Windows. Remember that? Microsoft said Windows 10 was the end of the specific version release of Windows. That survived right until the time their latest attempt at a mobile OS failed miserably and was rolled into Windows development, giving us the immovable taskbar that everybody despises.
Rumor is Windows 9 got skipped between 8 and 10 because lots of software check for a "Windows 9" string or similar as a Windows 9x version check.
I am inclined to believe Microsoft looked into it, was horrified, and then nothing more was said as they quietly moved forward a number.