Whenever there is a surplus in demand, the PSM builds up a reserve of BUSD from arbitrageurs minting MOR at 1.001 BUSD and selling it on ApeSwap for a profit. These BUSD reserves maintain the peg when there is significant sell pressure. As long as there is BUSD in the PSM, the price of MOR can’t go below 0.99 BUSD. And if it did, it would be arbitraged away.