The thing is, in my apps, I’ve turned off all sensitive categories in AdMob/Sense, and some risque ones still show up every now and then.

Whenever users report these to me, I first prove to them that I have indeed disabled such ads (screenshots of the dashboard), and then I straight up tell them to use ad blockers if it bothers them too much. Or at least use the report button in the ad itself.

Google’s detection is pretty good but not infallible.