It seems like it's only for a testing period though, as Valve did not make any announcements on it.
Valve is seemingly trying out a new feature on their digital distribution platform Steam, which will make the process of handling beta phases of games easier for both developers and testers. A simple button on the game's page will allow beta testers to sign up for test access. The button has been discovered on Total War: Elysium's Steam page, but could be hidden in other games' title pages as well. There are just so many games to be discovered in Steam!
This functionality will be a blessing for developers as they no longer have to plan an elaborate distribution and access control mechanism when it comes to allowing players for alpha, closed beta, or open beta phases. Hopefully, this means new games will be released faster, and with fewer bugs!