I don’t think they would actually say that. I think it would just be, once you’re at the ATM or the counter, “Oh, I’m sorry, we have a withdrawal limit today.”
This would prevent panic.
I agree, except that HSBC is one of the most important banks to HK. Their symbol is on the currency. If there is a limitation on ATM Withdrawals, I suspect it's with smaller, more fragile banks.