Treasury bonds are not a safe haven. The Federal Reserve will own all the Treasury bonds, as well as most other U.S. dollar denominated debt. The problem is that the tens of trillions of dollars the Fed will print to buy all those bonds will be practically worthless. Gold is the safe haven.
Real bond yields will plunge as inflation soars. Normally rising inflation would push up nominal yields to compensate buyers for the erosion of their purchasing power. But since the Federal Reserve is buying to keep nominal yields from rising, the entire bond market is about to be monetized!