"Is it me or is MS getting desperate now?"
Yes, it looks some sort of desperation -" we couldn't move enough people to Windows 10 using the free bait, so we have to find other ways" (maybe without slurping you would have achieved better results).
This would be the first version of Office to run only on a single Windows version in many years. Anyway, the "mobes approach" on PC won't work. But "monodimensional leaders" like Nadella can't really look at the big picture, only at the narrow self-imagined world their little brain can understand.
He's just inviting more and more people to abandon Windows for alternatives. He should have understood that where alternatives become good enough, Windows can't dominate - and many are already used to a non Windows world.
Alienating actual customers just because they didn't drink the last kool-aid may have a bitter price in the future.