This is false.

https://www.eurogamer.net/its-extremely-frustrating-and-also-fcked-up-one-of-the-worlds-best-indie-studios-is-facing-shock-closure-following-confounding-steam-ban

They submitted to steam, who asked for a preliminary build of the game (one would assume due to concerns about the content). The build provided included a small child reading a naked man like a horse.

Steam denied the game based on the inclusion of CSAM, and advised the devs directly of this decision in what the devs call “an automated email”, as if steam is out there personally hand writing rejection letters for every failed game out there.

The devs claim to have changed the scene, but it seems that Steam has a zero-tolerance policy on games that feature CSAM. And, I mean, Fair.