Also probably just defederating from servers that allow unmarked NSFW or are bad at enforcing it. I don't often stumble upon NSFW content on my parts of the fediverse, and if I do it's almost always marked so that it is blurred and could be filtered out.
I fully expect Meta to use AI to help them identify users to block and servers to defederate from though - it's going to be interesting to follow.
I specifically follow porn hashtags on my mastodon account, and I don't see all that much NSFW posts. So Meta probably doesn't have that much to worry about.