No, he didn't. The $10 billion is a part of the CARES act. Which is a loan that the USPS has to pay back.
The CARES act is still sitting on the desk of one Senator from Kentucky.... who just went on vacation. So, this quote: "“If we don’t make a deal, that means they don’t get the money. That means they can’t have universal mail-in voting; they just can’t have it.” is all about that $10 billion.