Need to change this back, or exclude it for admin-created accounts. This throws a wrench into development- when you're setting up content and content sections to belong to different people, you usually don't have a complete user list yet, because even if you did, it would probably change before rollout. So the last thing you get is your list of users.
So usually when you make your faux authors and editors so you can test out the restrictions and do the site demo, you use a single email set up for the purpose. As of 2.8's change, I now have to set up a different email for every single user account I set up to test a site? They're all authors, editors and contributors being created by an administrative account, so this is serving no purpose.