@elmer:That's where the "I don't know" come from.
Is true that the sales for Office in Windows/Mac is good enough, but if indeed adding Linux to the share require just a little compatiblity fix budget and the budget to create new test cases only, it may seems tempting for the marketing folks to extract cash from that market too.
And I believe commercial oriented versions (non-free versions) of Linux could be interested to bundle MS Office instead of StarOffice or KaiOffice (both office software are not free). 100% compatible rendering of Office documents can make the distro a strong choice to these "companies using Linux as required by governement policies or coporate rules, etc".
Office team is a seperate company in Microsoft, so their marketing effort need not take "lockdown customers to Windows" into consideration.