Ah it was Word 2.0 vs Word 6.0 (which was roughly Office 3.0 vs Office 4.0)
Word 2.0 shipped on a lot of Windows NT computers with Office 3.0 and these were the days when there weren't forced updates and you had to pay so it hung around for ages.
I think you're misremembering or mistyping the numbers, unless Wikipedia is wrong?
https://en.wikipedia.org/wiki/History_of_Microsoft_Office