Holdings are Long positions . A short can't be HELD. It's a borrowed stock which is immediately sold to someone else.
This is completely wrong and shows a serious lack of understanding regarding Longs and Shorts!!!
A shorter can hold his borrowed shares for as long as he wants seeking a profitable place to Buy-to-Cover. The only reason that would force him to sell would be because of a Margin Call.
Just as when you go long on margin, it's easy for losses to get out of hand because you must meet the minimum maintenance requirement of 25%. If your account slips below this, you'll be subject to a margin call, and you'll be forced to put in more cash or liquidate your position.