I don't know or recall the details well enough to be sure, but it's possible that they were, in fact, testing the backups but had never before exceeded the 2GB

I don't know or recall the details well enough to be sure, but it's possible that they were, in fact, testing the backups but had never before exceeded the 2GB limit. Knowing that your test cases cover all possible circumstances, including ones that haven't actually occurred in the real world yet, is non-trivial.