Sorry but you are breaking it in two parts, it is a single sentence the "that is" part signifies that the incest and other genres are prohibited only when they are non-consensual.That's not what it is saying. It is saying that ALL of the following are prohibited:
- Incest
- Necrophilia
- Fetish content that is hard to distinguish from non-consensual sex
The non-consensual part is a separate item on the list. All three of those are not allowed. It even goes on to specify in the next paragraph that some incest is allowed in certain contexts and cites examples like Game of Thrones. Which means that incest on the whole, especially in the context of games like DmD, is not allowed.