The lines are blurred here between an exchange and a bank. Exchanges normally don't hold your personal assets. Bank of America holds my equities. I trust them to execute the trades on my behalf on the NASDAQ exchange. If something goes wrong with the exchange, I trust Bank of America to have my back (or at least trust that I have legal ramifications if they don't).

With Bitcoin the entity holding your assets and operating the trading mechanisms are generally the same company. This leaves a customer in a weaker position and could allow the exchange/brokerage/bank to get away with shadier practices. They can do things like delay the execution of a transaction until it better benefits them. Or they can unillaterally suspend the ability to withdraw funds with no advance notice, just as what is happening here.

I think you are being disingenuous if you think your bank don't do similar things. Ever had to bank a cheque? When you deposit it into your account they immediately debit the account of the person that wrote the cheque, does it appear in your account for spending immediately? No you wait 3-5 working days, what happens in the interim? The bank hold it and accumulate interest on it and then you are allowed access to it.

And if the person who had their account debited would drop to a negative balance at the end of that 3-5 days the check will bounce and they will be credited back the amount of the check.

Edit: You of course do not get the funds in the case they are credited back to the original person at the end of the 3-5 days, you do probably get a fee for trying to deposit a bad check though!

Precisely because it's an exchange and not a bank that any delays in transactions are problematic. I don't think the comparison is fair.

FYI: It takes 3 days to get USD out of TD Ameritrade too.

5+ days for Fidelity

...TD Ameritrade is a bank.

I was referring to a trading account at TD Ameritrade. I cannot speak of their banking capabilities nor do I see how it is relevant.