https://www.cnet.com/news/microsoft-and-razer-working-on-keyboard-and-mouse-for-xbox-one-reportedly/

The presentation fell into the hands of Windows Central, detailing what the programming interface (API) for the support looks like and potential concerns -- particularly the potential to change gameplay balance between KB&M and controller users in multiplayer games and ways to counter it. The recommended solution is matchmaking only between similar controls and monitoring it throughout the game.

The API -- which is the much same as the mouse API on Windows 10 -- only supports USB and dongle-wireless mice, not those which connect by Bluetooth or use custom drivers. A Bluetooth mouse makes no sense in this case, anyway.