It's funny, because it used to be that everything Microsoft did was in furtherance of the 'Windows über alles' philosophy, that Microsoft can only win if everyone else loses. Within that philosophy, though, there was no direction. You drank the kool-aid, and then your team just did whatever; see the famous example of the Office manager hating the idea of tablet PCs and refusing to support them in Office. Everyone was working towards the same goal (the Windows hegemony) but doing so in a disorganized fashion.
Now, it seems like Microsoft's new direction is 'stay relevant and make good things'; everyone is working in the same fashion (make new, relevant technology), but there's a lack of coherence. Microsoft making such a fantastic iPad app as Office for iPad is certainly weakens Office on Windows, Surface, Windows 8 RT, etc., but it also means that Microsoft will still be relevant even if any one of those fails. Likewise, it makes no sense for them to make a version of Office for Mac and (intentionally) cripple its compatibility to hurt the Mac's image.
Now that users aren't (and can't be) forced to use Office on Windows, the Office team needs to keep their product relevant and their revenues flowing; that means covering as many platforms as possible, and ensuring proper interoperability between them.
Basically, the Office team's job now is to ensure that Office survives, not to ensure that Windows 8 or the Surface survive.