Very good point on the roll-back.

However in terms of the hack, Bitcoin is slow - most exchanges require a few confirmations so it's 30+ minutes to land a deposit in Coinbase/Binance at minimum, and a transfer that huge would instantly set off alarms. Seems unlikely that they would be able to unload that much.

Coinbase would definitely go into buy-only mode during a major crash but that just means people would scream while they watch futures/perps go to zero.

"If you're first out the door, that's not called panicking."