I don't think that correlates with a kid having to do homework. I agree there are professions that "require" work to be done regardless. I am a software engineer and occasionally take it home with me. I think schools are overstepping their bounds to assign summer homework.
How many university undergrad programs do that? None I know of.
Freshmen at my alma mater were expected to read a book (a collection of short stories, sent by mail) before arrival.