Introducing XWine1, an Xbox One translation layer for Windows PCs. Currently six games are fully playable, with others reaching logos and in-game. More news to come.
There are xbox360 games that aren't on PC, and if this also handles the XBone's backwards compatibility, then yes there are Xbox games that aren't available on PC currently
Namely I've been waiting to play Lost Odyssey on PC for over a decade
At the very least, there's Rare Replay and Halo 5. Plus this was like the very end of the era where some third parties didn't make PC ports, so I'm sure there are some stragglers there.