We really need to get to a point where companies see holding identifiable data as a big risk that they only want to undertake if absolutely needed
There are still some minor issues with doing it that way, but it's much, much better than storing plaintext email addresses. I don't know of any other sites doing it this way, but I wouldn't be surprised if others have thought of the same method.
During registration you can just leave the email field blank and click "Next" to skip giving one, even though there's no indication at all that it's optional.
The site also annoys you constantly now to add an email address, but you can ignore or adblock that.