I was amazed by this too. Why focus on how one pronounces it rather than the mathematical properties of asymptotic behaviour (i.e., that one gradually approaches but never reaches something)?
Yeah, this is a little odd. But in the writer's defense, I read a lot more than I speak, and I often comically mispronounce a useful word when I have to use it in speech, so while I'm familiar with this particular word, I do wish writers would do this with words a little more often than they do.