As spotted by SteamDB creator Pavel Djundik, United States Patent 11123634 was filed by Valve in March and published yesterday. It describes a Steam mechanic called "instant play" that would allow users to start playing a game as soon as it starts downloading.
https://www.techspot.com/news/91366-valve-looks-set-introduce-play-while-downloading-featuring.html?utm_source=dlvr.it&utm_medium=blogger
https://www.techspot.com/news/91366-valve-looks-set-introduce-play-while-downloading-featuring.html?utm_source=dlvr.it&utm_medium=blogger