So here's my interpretation of this last move from Elon and how it is designed to screw the shorts. Please correct me if I'm wrong.
In a normal stock split, one share automatically becomes 5. Say, Chanos borrowed a share from me and sold it. Post split, it is automatically recorded that he borrowed me 5 shares on a post-split basis. Whenever he chooses to cover, he can just buy 5 shares for the price of 1 and return that to me.
When it is done via a stock dividend, things become dark. Shareholders actually receive 4 new shares for every share they own. Post split, it is still recorded that Chanos owes me only 1 share. The sequence of this whole affair is as follow:
I owned my share
Chanos borrowed my share, now I'm no longer the holder on record
Chanos sold it to someone else, now neither Chanos nor I is the holder on record
So on 8/21, neither one of us is entitled to the 4 new shares. Yet, Chanos still owes me only 1 share, which means he has to come up with those 4 shares to deposit in my account at the end of August. So, he is forced to cover.
Although that doesn't stop them from re-shorting the stock once it's all said and done, but a forced covering is still a thing of beauty.