Yes they can of course, my comment was in relation to gold and silver. If you are unfamiliar the gold and silver markets they are short selling them to the tune of trillions, metals are an old market, crypto is an emerging asset class. Gold has been accumulated by powers throughout history and when a new power comes along they simply steal the lesser powers gold at the end of wars. To accumulate the Bitcoin needed to short sell on the scale that is seen in the metals markets would send Bitcoin through Jupiter on a galactic journey out of our solar system. So while yes they can and are shorting Bitcoin but not anywhere near the scale seen in the metals markets.