Which three publishers?
You mean like Kagura? That's grey area business operation.
They take out the hentai element out of the game, then publish the game as non-hentai game on Steam.
Players then download the hentai version dlc from Kagura website.
Of course, Kagura take commissions from providing service like that.
It's very shady because Steam gives a blind eye when there are publishers doing this. Then bans indies for doing this without publisher.