As you note, the Fed lending policies do act as a money source (when increasing supply) and also as a money sink (when decreasing supply). That doesn't invalid

As you note, the Fed lending policies do act as a money source (when increasing supply) and also as a money sink (when decreasing supply). That doesn't invalidate the parent point that taxes have nothing in common with a money sink, since that mechanism (unlike Fed) doesn't affect money supply but rather simply moves it to specific purchases/institutions.