This is not a safety filter. The owner/author is explicitly geolocation IP blocking UK users:

https://aphyr.com/posts/379-geoblocking-the-uk-with-debian-n...

Most likely it's a protest. Badplace passed Badlaw, so residents of Badplace can't see my content, so nyah!

But, topics of a sexual nature—nothing really NSFW, just mentions of various fetishes that online people have developed and popularized, and the possibilities for AI to realize those fetishes and potentially spawn new ones—are discussed in the blog post, so it may be illegal to present to minors under the OSA.