10% of prodigies becomes 10% of elite, whereas (whoknows)% of (general_population - prodigies) becomes 90% of elite.
How big is elite? How big is prodigies?
Well, for a start, I guess we can assume that size of elite == size of prodigies, because 10% == 10%.
But what is that size compared to general population?
If it's 1%, then 99% of muggles compete for slots in 0.9% of the population, so, hey, a prodigy is 11 times more likely to become an elite than a muggle.
If it's 0.1%, then a prodigy is 111 times more likely to become an elite than a muggle.
If it's 10% -- well, that's kind of stretching the definition of both prodigy and elite, isn't it?
tl;dr -- article is crap; research probably is, as well.