We already review all content that is on our site - if you have content that needs the mature filter or not, as long as your content follows app guidelines, it will stay on the app. It is against anybody's interest to remove series without reason.
It was grouped together for other reasons - I apologize that it's coming across as if this is going to be used against creators.
Curse words are a bit of a fringe issue - it really depends on your audience for this one. If you have younger readers that would be surprised by cursing, you should add it. If your audience skews older, it isn't necessary.