There certainly is an advantage if you're worried about the stability of the financial system. Banks can fail, corporations can fail, if the US government fails

There certainly is an advantage if you're worried about the stability of the financial system. Banks can fail, corporations can fail, if the US government fails to repay then things are probably so bad you're probably already dead... If you're worried about getting repaid or you're desperate to get your cash out of whatever it's currently in and into something safe and liquid then short term treasuries are probably your answer. But like I said I don't know if that applies to auctions like this, auctions are not the same as the general market so it may just be a fluke.