In general, that is the rule.
The cynic in me couldn't help but notice that an article with the original title "One of a Kind: What do you do if your child has a condition that is new to science?" has been on HN's front page for a day now with an alternate title.
For some reason, the same mods who removed "Feynman" as "click-bait" that is "not the title from the article" don't seem to have a problem sticking with the alternate title "Thanks, HN: You helped discover a disease and save lives" [https://news.ycombinator.com/item?id=8050106].
Why would there be an "exception" to the policy of discouraging submitters from editorializing headlines? Even if the submitter had a personal connection to the material (which isn't unusual), the guidelines should be respected.
Also, the headline modifications in that case were not made with the same intentions that other (harmful) headline modifications are made.