. . . it's about to venture into even stranger, darker territory with Horses, an unsettling first-person narrative horror adventure set on a farm whose livestock consists of naked masked humans.

"While we strive to ship most titles submitted to us," Steam's automated response read, "we found that this title features themes, imagery, or descriptions that we won't distribute. Regardless of a developer's intentions with their product, we will not distribute content that appears, in our judgment, to depict sexual conduct involving a minor. While every product submitted is unique, if your product features this representation—even in a subtle way that could be defined as a 'grey area'—it will be rejected by Steam."

. . . the studio now suspects a work-in-progress scene from day six of Horses' narrative (the game follows the player across 14 days as they work as a hired hand on the farm where the "horses" are held) might be the culprit. In the early build reviewed by Valve, day six featured a scene in which a man and his young daughter visit the farm. The daughter wants to ride one of the horses, resulting in an interactive dialogue sequence where the girl rides on the shoulders of a naked "horse" while it's led by the player. "The scene is not sexual in any way," the studio notes in its FAQ, "but it is possible that the juxtaposition is what triggered the flag."

. . . notably, the final version of Horses has been reviewed and approved for distribution across numerous other PC storefronts, including the Epic Games Store, GOG, the Humble Store, and Itch.io. And while Horses won't be launching on consoles due to porting costs, Pietro says the console makers who've seen Horses have said they'd be "happy to have the game on [their] platform".

From the description of the scene which seems to have triggered the refusal to platform the game, the studio probably pushed the envelope too far.