Three months ago, the Treasury surprised markets when in its quarterly borrowing forecast, it revealed that in the first calendar quarter of 2021, it wouldn’t need to borrow as much debt as it had recently because the Treasury’s cash balance (held in the Treasury General Account, or TGA, which is simply the Treasury’s cash balance held at the Fed) would plunge to just $800 billion, down a record $929BN from $1.729 trillion at Dec 31, 2020…