Some of the shared assets and tools that allow games like this to be made at all are not, last I looked, allowed on Steam at all. Until that changes, don't count on it.
If I were a small-shop dev, I wouldn't do it anyway. I worked in the Valley in a legal capacity, and even for me, it was nearly impossible to get an actual person at Steam, even when it was them that approached us. I have to think they treat small-shop games like this (adult or otherwise) the same way Apple and Google treat app submissions: you show it to them, they own it.