Office was already slowly adopting UWP, some of the new WinUI 2.0 components came from them, in a spirit similar to how Ribbon went from Office into Windows.

Then came Project Reunion, with the whole reboot, that five years later still hasn't reached feature parity, seems most of the team is gone, and they are even open sourcing it, with hopes that the community fixes the bugs that a $4 trillion valued company doesn't care about.

Of course only people on the Windows team care about this, because their salaries depend on it.