Seems to me it still makes sense to only hire people who program in their free time... if your real goal is to hire people willing to do a lot of overtime work. (I am not saying this is a good thing to do.) Things that prevent you from programming in your free time are more or less the things that would prevent you from working overtime.
Or it could simply be thinly disguised ageism. "Hey, I am not saying we shouldn't hire people who have kids... I am just saying I don't trust people who are not passionate enough to write code in their free time!"
