That rule seems problematic. You cite the rule, and then the last line of your comment explains that you've violated the rule.
As another example, I recently read a Factorio blog about how they do map generation, and there were a lot of technical details any aspiring game developer would be interested in, even if they don't play Factorio. The title of the blog post was "Maps 2.0" which would be meaningless as a HN title. Something like "How Factorio's procedural map generation works" would make more sense for HN, but would require breaking the rule. What should be done in this case?
It's problematic if you expect the rules to work like code; they don't. It's less problematic once you understand than HN has always been a spirit-of-the-law place, not a letter-of-the-law place (https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...).
From that perspective it's easy to see how the submitted title was breaking the rule, and how shortening a title so as to fit HN's 80 char limit is not breaking the rule, as long as one doesn't shorten it in a misleading or linkbait way.
(Re your Factorio blog question, I'd have to see the particular article to answer that.)
As another example, I recently read a Factorio blog about how they do map generation, and there were a lot of technical details any aspiring game developer would be interested in, even if they don't play Factorio. The title of the blog post was "Maps 2.0" which would be meaningless as a HN title. Something like "How Factorio's procedural map generation works" would make more sense for HN, but would require breaking the rule. What should be done in this case?