It looks as though adult games are being temporarily withheld from Steam while Valve continues to implement tools allowing for players to filter games they aren’t interested in from their own personalized feeds.
Valve previously asked developers to remove "sexually explicit content" from their games or risk having them removed from Steam, but quickly retracted those changes after backlash from the development community.
Instead, the company said it would "review" games for content violations (although it isn't clear what counts as a violation) before circling back with developers.
"Yes, some titles are being held. We will have more info on this soon," a representative from Valve said via email.
Developers Love in Space tweeted back in June announcing they had completed development on the adult visual novel Shining Song Starnova and were waiting for Valve to approve the build.
However the studio tweeted again last week, updating players that they had heard back from Valve but Shining Song Starnova would be delayed.
"The summary is that they are working on new features to give people more control over the content they see and SSS has been identified as needing these features in place before it can go live on Steam," the tweet writes.
It isn't explicitly clear what Valve's criteria for delaying games are, or what the proposed timeline for rolling out these new features is.