The information is incorrect. If you are short on the ex-div date, you owe the dividend. You do not have to cough up the cash until the dividend payout date. So, even if you cover your short position between the ex-div date and the payout date, you still owe the dividend.
Mystery, do you know that for a fact? Can I confirm that information somewhere online that you know of? The reason I question it is because I have owned shares in a company before the ex div date, but sold between the div date and the actual payout date, and I did not receive any dividend cash, so I assumed it would work the same way in reverse.