Note this happens all the time to people who vest stock, and then before the next trading window the stock tanks in value. The employee owes income tax on the stock they vested, at the time the stock was granted, then have capital losses for the drop in share price. Losing 90% of the value of say $1,000 of stock, you could still owe something like $300 in taxes on what is now worth $100. This is the normal world for employees.

I’m not totally sure why we would want billionaires to shoulder less downside risk than their wage earning employees?