Quantitative easing also involves the use of printed money by central banks to buy government bonds. But not everyone views the money used in QE as helicopter money. It sure means printing money to monetise government deficits, but the govt has to pay back for the assets that the central bank buys.
It's not the same as bond-buying by central banks "in which bank-owned assets are swapped for new central bank reserves."
Helicopter money is also different from a central bank directly financing the debt of a government.