Here is a simple way to demonstrate the point of the article. If I deposit $100 in a bank, the bank can lend out around $90 to someone else (fractional reserve banking). That person now deposits the money at another bank, and the "money supply" is $190 instead of $100.
On the other hand when a central bank "prints money", they use it to buy assets with an equivalent value, so there is no net transfer of wealth done by the central bank. That assumes they don't affect asset prices, which not a great assumption.
The way central banks affect the money supply is through interest rates to change the supply and demand of private loans that banks make, which indirectly affects the money supply.
On the other hand when a central bank "prints money", they use it to buy assets with an equivalent value, so there is no net transfer of wealth done by the central bank. That assumes they don't affect asset prices, which not a great assumption.
The way central banks affect the money supply is through interest rates to change the supply and demand of private loans that banks make, which indirectly affects the money supply.