I think they're more looking for a sign that you had an early and therefore natural curiosity to tinker with the mechanisms in the world. Not "CS" per se, but just... computer tinkering. If your family couldn't afford a computer, IMHO, if you at least, say, took a clock or motor apart or something, that would be a good indicator, too.
By the way, this has been brought up as the reason for the dropoff in the women who enter CS curricula in college. Ever since home PC's became affordable, freshman CS classes have basically assumed prior (and thorough) computer experience, and many women who might otherwise become good programmers, for whatever reason (society influence, etc.) have had waaaay less hands-on time with computers than boys, when they become freshmen.
That said, I have met some excellent programmers who started out doing something that is superficially completely different (musicians, for example).
I imagine that it depends on the school but there's probably some truth to that. I've taken a couple of "Intro to Programming" type classes from top schools. I found the material quite manageable--but then I have a moderate amount of programming experience even though I don't do it for a living. I'm pretty sure that if this were the first time I saw a computer command line or wrote code, I'd have been lost. Freshman physics at those schools may be challenging but it doesn't assume a whole lot of prior exposure (other than an appropriate level of math).
I never had any distinct interest in computer science. My original interests were physics and art. In fact, I would say those are still my strengths over all. But I went into CS after I found it interesting in regards to what a person can do with a computer with little effort (in as much as the tools involved).
By the way, this has been brought up as the reason for the dropoff in the women who enter CS curricula in college. Ever since home PC's became affordable, freshman CS classes have basically assumed prior (and thorough) computer experience, and many women who might otherwise become good programmers, for whatever reason (society influence, etc.) have had waaaay less hands-on time with computers than boys, when they become freshmen.
That said, I have met some excellent programmers who started out doing something that is superficially completely different (musicians, for example).