Well, doing a high school olympiad didn't get me into the university I wanted, so why would a university-level olympiad get anyone into the job they want?
It doesn't work as a credential unless it actually produces results.
Uh.... the IOI/IMO/etc. are for high schoolers. Doing well on the IOI (bronze or higher medal) will get you into any university you want. Doing well on the IOI is something that you'd also put on your app if you were applying to a PhD in mathematics.
Ah. I see what the problem is. The IOI started in 1989. The US first participated in the IOI in 1992, and has sent a total of 65 contestants. The first opportunity I might have had to be selected would have been 1993. My AP Computer Science teacher was the baseball coach, who presumably wasn't looking to sponsor any other extracurricular activities.
I had therefore never heard of it before this thread, despite it being around for 27 years now.
At the time I was in high school, US Science Olympiad, Indiana Academic Super Bowl, and the Rose-Hulman Math Competition were about the only games in town. And it was a big school. We might have had a US Chemistry Olympiad team if the chemistry teacher wasn't a few moles short of a balanced reaction, if you know what I mean. The biology and physics teachers were the Science Olympiad sponsors.
I'd think that even just being on the IOI team would be enough to get you accepted anywhere, given that you would have to be one of the top 4 students in the US for that year (by the best screening process that several university professors can manage).
It doesn't work as a credential unless it actually produces results.