nope, it's a game that has adult-only content, and steam is only allowed to sell it to adults, but refuses to implement any age checking, which germans has mechanisms for
what you mean is steam's age *warning*, which does not comply with germany's age checking laws, and thus is not suitable to allow steam to sell adult-only content. look, i'm german too, and i'm a developer too and familiar with the industry. there is no ban. it's strictly the limitation of selling adult-only things