Insiders who have locked up stocks but still want to sell could presumably just short the stock and take out a loan secured on the stock to get the financial effects of selling, without actually selling...
I wonder if that's what's happening with ~$1T of stocks currently locked up...
You don't "short the stock" by taking a loan secured by it.
Insiders aren't allowed to short a stock. It's against the law.
What happens if you get margin called in this scenario?
If anyone knows of a broker who will let you withdraw the proceeds (cash) of a short sale, I will buy the name of the broker off you. I'll also let you know why I would pay for this (although you may already know anyway, hah).
I spent a week researching this talking to fidelity, schwab, IBKR, and Robinhood, none would allow it.