All the projects I checked are properly marked NSFW. Neither NSFW games nor profiles with NSFW games on them show up in search, but if you click a direct link to a NSFW game, you have to click through a warning to actually view it, so your settings are still respected even if you didn't discover the game within itch.io. Profiles and collections with NSFW content don't get that click-through warning.
Also, the particular issue I had was with a collection displayed on my profile that contained a game with a NSFW thumbnail image, and I'm not sure if having collections on your profile that contain NSFW games would delist your profile from search if you haven't actually released NSFW games yourself.