The actual mechanism is one where the central bank expands its balance sheet beyond its normal rate of acquisition of government debt. That creates a higher level of settlement balances in the banking system. So it's liquidity in the sense that you describe.
That liquidity is then available to offer reassurance. I like to think about the bubble that we had. After the bubble burst, there was a crater and the central banks filled the crater up with liquidity so we could row our boats across it.
Once across it, then it's okay to take the liquidity out. So that liquidity does perform the function that the first textbook might describe as effectively printing money, because both sides of the balance sheet are expanding. But it is not literally the printing of actual money.