UPDATE (9 September/ 6:20 PM):
As it turns out, the stipulation that was thought to be new was there as far back as 2017. YouTuber SidAlpha verified this using his suggested Steam developer account.
This means that this is not a case of Steam preventing more episodes similar to Metro Exodus. Instead, this means one of two things. One is either Valve is aware of what Metro Exodus’ publisher Deep Silver is doing, but is not taking any legal action. The other may be that Valve has forgotten that it has this stipulation in the first place. Either way, only Valve will know.
ORIGINAL STORY (8 September / 4:14 PM):
It’s probably not news to anyone that the Epic Games Store is snagging up exclusives left and right. So far Valve just allows games being announced on Steam, only for them to later be an Epic exclusive. But the company may actually been working hard prevent that from happening again.
A Reddit user has found that Valve has added a new item in the Steam Distribution Agreement. It’s a complicated couple of sentences, but it essentially means two things.
One is that if a developer or publisher has not made a Steam page for its upcoming game, then when it does it will have to release the game at the same time as on other platforms. The second is that if a game is already released, then developers and publishers can create a page for it no earlier 30 days before its release on Steam.
Normally, this document will never be seen by the public, as you have to sign up as a developer first. But it implies that Valve want to stop developers and publishers from using Steam just to advertise their game. Metro Exodus comes immediately to mind as an example, following its last minute announcement as an Epic exclusive.