"otherwise the site owner would have to check if their content is considered adult in the UK and implement something"
IMO a small blog website is not going to get pulled-up for this - it's about the author making a point. They're entitled to do so of course.
Never know when one of your posts might gain serious traction. Not worth the risk. Very easy to find many examples of people making decisions thinking “I/we will never be big enough for that to be relevant” only to be haunted by that decision later. Classic example: partnership agreements/contracts between friends and family on small endeavors.
> IMO a small blog website is not going to get pulled-up for this
Well, maybe not the typical engineering blog but I think if you're a puritan some posts/texts from Aphyr probably reaches borderline "adult content", so I'm not that surprised Aphyr rather play it safe and also make a point at the same time.