From what I understand, Itch doesn't block such content, it just hides it.
If you explicitly look for it, it is normal and expected that you can see it.
You must actively and explicitly search for said content, if you try to enter said game, you will get the warning window, which you can skip at will.
Again, it's expected behavior, adult content is not blocked, only hide.
What should not happen is that it shows you that type of content if you are not looking for it, for example, if you only search for 3match, then it should not list games that are 3match+NSFW