In that case, I'm not sure. The people reverse-engineering the algorithm say they aren't quite sure if that's because the system hasn't shown up in MacOS Developer Previews yet (where it has in iOS and iPadOS), or if that's because they are referring to the generic nudity detection instead of the database matching system.

For now, the security experts looking at this say that the nudity detection model is on all platforms, but the database matching in iCloud Photos is only on iOS and iPadOS and it's unclear whether it will come to macOS.