It's a representative subhead. Those are a legit alt when the article's main title is baity. (Lots of past examples: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...)
People often think that HN insists on using the original title but that's only half of the rule: ""Please use the original title, unless it is misleading or linkbait; don't editorialize." - note that word 'unless'.