You can contend that, but it isn't what happened.
" ... story of Windows dates back to September 1981, when Chase Bishop, a computer scientist, designed the first model of an electronic device and project "Interface Manager" was started. It was announced in November 1983 (after the Apple Lisa, but before the Macintosh) under the name "Windows", but Windows 1.0 was not released until November 1985. ... "
http://en.wikipedia.org/wiki/Microsoft_Windows#Early_versions
Did it look alot like the Xerox PARC GUI ? No. It is a bunch of revisionist history though that only Apple was aware of the kinds of interfaces being developed at PARC and other research labs at the time.
1989 is really Windows 3.0 and yes that is what "took off" in the Marketplace to outpace the Mac as being the more widely used GUI.
1989-1990 was where IBM and Microsoft broke up. OS/2 also started well before 1989
" ... The development of OS/2 began when IBM and Microsoft signed the "Joint Development Agreement" in August 1985.[3][4] It was code-named "CP/DOS" and it took two years for the first product to be delivered. ... "
http://en.wikipedia.org/wiki/OS/2#1985-1988:_Enthusiastic_beginnings
Microsoft gained leverage with Word/Excel on Mac OS in the transition to Windows 3.0 in part because the other Application providers let Microsoft largely have the Mac OS base without as much competition. Most of them were not beating heavily on every horse in the race ( DOS, Windows, OS/2, and Mac OS ). Certainly Microsoft knew somewhat in advance that they were going to pull the rug out from under OS/2.