An elegant example of just how broken some interview / hiring practices are.
In this case, and in most interview cases, there's already been some vetting done via resume/portfolio/phone, and face to face interviews are as much about personality and team fit as they are about technical competence. Being able to demonstrate that you can think about others socially, include them in to a small ritual, and do it in a way that's memorable without coming across as too cheesy (I don't think I did) is... dare I say, a skill.
I've definitely been on the interviewer side of the table, and if someone had brought in some cookies to munch on, it would bode well. If that's the only thing they do, and they still suck during the interview, no job.
I'd done this a few times over the years, and in a couple cases never even got a followup call back. If it was because of the cookies/cake/snacks/whatever, then I'm glad I don't work at a place that's so uptight/rigid that they can't take some fun.
FWIW, I didn't take a job after that interview, but was offered one.
That makes it a good example of how little skill and ability mean in the interview process. That's broken; say the right thing or do the right thing and you're in.
Knowing what those are and how to do this is, by most measures, a good skill to have.
"you were called not because any ability of yours stood out, but because you did the right thing to suck up on the right day".
In that case, the birthday thing was a total fluke, and not really that big a deal, more a happy coincidence. But as I mentioned before, I wouldn't have had an interview in the first place without a baseline of skill/ability already demonstrated through other means (online portfolio, resume, phone screen process). The ability to make a positive memorable impression is, imo, an ability that did stand out.
I would also like to point out that an ability of your parent poster clearly stood out, that of making themselves memorable. Hiring is a multivariate problem, focusing on just one of those variables could be the most broken solution within the space.