Not necessarily. Take the situation where a large player wants...

Not necessarily. Take the situation where a large player wants to "free carry". If they dump part of their holding into the market to achieve that they know it will depress the share price. If they trickle into the market the price might go backwards for some other reason while they are executing their strategy. So, using their own stock as collateral, they'd short as many as they are selling. Then they close the shorts at the same rate as they are selling shares on market, until their strategy is complete. They have taken the risk out of their transaction.