You can't create an account with them, transfer in $50M worth of stock, and transfer out the USD all in the same day.
Frankly, I'd be fairly surprised if you could even transfer $50M into a self-serve account the same day your account is created - likely some compliance and human-intervention guardrails would slow this further than transferring several thousands of dollars worth of stock. But even so, USD transfer is going to take at least a day.
