And I would guess that likewise there are still a lot of people that don’t know this.
Also, sometimes one might not realize that the title got changed until it’s too late to edit the title of the post.
Edit to add: Bottle's own FAQ says so: https://bottlepy.org/docs/dev/faq.html#what-about-flask
More seriously, HN should instead display an instruction after submitting, informing that the title was changed and that the submitter should check the change and edit if necessary. The issue is that most submitters either don’t seem to notice that the title changed or don’t hit on the idea that they can edit it after the fact.