If Tesla stock drops and his loans against Tesla stock go negative, he'll be forced to liquidate more shares to make up the difference to keep the loan afloat... this would then lower the value of the stocks even more, and the positive feedback loop could let all of the air out of his imagined wealth.
In other words - He has effectively sold shares at a price by borrowing against them... if the price falls, he'll have to do something to make up the difference... which is about the same thing as a short-squeeze for him.
If Tesla stock drops and his loans against Tesla stock go negative, he'll be forced to liquidate more shares to make up the difference to keep the loan afloat... this would then lower the value of the stocks even more, and the positive feedback loop could let all of the air out of his imagined wealth.
In other words - He has effectively sold shares at a price by borrowing against them... if the price falls, he'll have to do something to make up the difference... which is about the same thing as a short-squeeze for him.