Maybe I'm misunderstanding something, but you can add filters to RSS feeds. What is proposed is pretty much just RSS, except for one specific item. Yes, it's more work on your side, but asking the creator to manage updates for whatever one thing any/every random person is interested in is pretty unrealistic, especially since the people asking for this are going to be explicitly not interested in everything else about the creator.
> There’s no AI to this. No magic. No problems to be solved.
Why would you not involve yourself in the new hotness? You _can_ put AI into this. Instead of using some expression to figure out whether a new article has links to the previous ones in the series / a matching title, you can have a local agent check your RSS feed and tell you if it's what you're looking for, or else delete the article. For certain creators this might even be a sensible choice, depending on how purple their prose is and their preferred website setup.