I have "Include Adult Items in Search?" set to "Yes" in my profile settings, but adult movies do not appear in the list of possible duplicates when adding a new movie. As I have not yet marked the new movie as "Adult" it makes some kind of sense, but it makes it harder to add adult movies. As an example I accidentally added a duplicate (that I reported when I discovered what I was working on) of https://www.themoviedb.org/movie/70518-here-comes-the-bride earlier today, because I had a source saying the new movie was produced in 2009 (that must have been an error or the date of some remastering), and that movie was not among the four suggested duplicates based on the title (and description).

I'm not sure what the best solution would be (the new movie/tv show also uses a completely different design, that could probably be changed), but I think including adult content in the search (for those of us that have that turned on in our settings, I'm not suggesting that those who haven't should see those titles there) would be a good thing.