Earlier quoted context omitted.
I don't think even the USPS can order your bank to transfer money to them, you would have to order it. As a result, I guess that the 'take it all back' refers to adjusting pay.
I'm pretty sure that the agreement I signed to enable direct deposit allowed for errors and overpayments to be removed from my account.
Even now, at my Federal government job when someone is overpaid we issue them a "debt letter" and then reduce their pay until the account is balanced. I assume it's because of the same reg/statute that fixes the clawback to 16.7%.