Here is the primary risk of why frontloading the US Treasury with ultra-short holdings is just asking for a capital markets/liquidity/solvency/sovereign crisis. So far in April, the US Treasury has redeemed over $484 billion in Bills. That's nearly a half a trillion in mandatory cash outflows, interest payments aside. In April the cash out for interest expense will likely be one twentieth of this. What people don't realize is that the Treasury in April was down to just $9 billion in cash. Unless the UST can roll its debt not on a monthly but now weekly basis in greater and greater amounts, the interest rate doesn't matter. All it takes is one semi-failed auction and it's game over as hundreds of billions in bills become payable.
When one adds the redemptions on non-Bill Treasuries, and we get well over half a trillion in redemptions in April alone. This is better known as a house of cards, balancing on an upside down ladder, located in a puddle of extra slippery oil.
Roll issue aside, the UST issued a net $113 billion in debt in April, coupled with a gross cash burn of 27 billion for a net cash outflow in the month of $140 billion. Add the $120 billion or so in coupons in the last week of April (which likely won't settle until May), and the UST will have a $260 billion in cash burn in April.