According to multiple outlet, some games on Google's Stadia streaming service are not rendered natively at 4K, like Google advertised them to be. Rather, some titles are rendered at lower resolutions and then upscaled to 4K once the data is sent to a gamer's Chromecast Ultra. This and a myriad of other complaints have left black marks on Stadia's first impression.
https://www.notebookcheck.net/Google-Stadia-upscales-games-to-4K-rather-than-rendering-them-natively-at-4K-as-advertised.443706.0.html