https://www.techradar.com/news/xbox-one-x-and-one-s-getting-1440p-support-in-the-near-future

Often regarded as one of the Xbox One X's most impressive features, supersampling uses the console's additional horsepower to provide improved graphical quality to your games when played on Full HD (1080p) displays.

At present, the Xbox One X downscales 4K signals exclusively to 1080p, meaning those with QHD (1440p) monitors are left playing at a much lower resolution than their screens are capable of – but not for long!