I don't remember take-home exams in the nineties when I did computer science. Is this really that common to start with?

Because it is not an issue if you don't do it in the first place.

The problem with take-home is similar to the problem I saw with open-book. Now, you were maybe biasing the results to favour people who can skim through the book more efficiently. It is not really about people using knowledge they absorbed. I hated open book -- it put me at a great dis-advantage because i was much better at slow absorption.