It IS true, for certain facial features. Go ahead and create some cute kid in CAS, give it pixie-like features, make it just sickeningly adorable - then change it to adult. Instant circus freak, I'm telling you.
Of course not all of them will grow up to look good. If you have one with, say, a monkey face as a kid, that sort of thing only gets worse.
Making them look good regardless of adult features because they don't get to grow up is fair enough.