"Let us say that: a bank accepts deposits and receive 1000 Btc from various depositors. They give loans, but owing to the fact that they do not have Btc or rather the codes that Btc are made up from, they can never lend more than 1000 Btc. If the bank lends 1000 Btc no depositor can withdraw any Btc; which means that 1000 Btc equals 1000 Btc and not 2000 Btc.
I'm sorry, I don't know how else to explain it. you're getting it wrong. I think you're confusing "central bank money/21 million coins" with money. bank deposits are money (by any reasonable) definition, the bank doesn't need to have all the "bitcoin codes" in order to have deposits on its books. they simply owe someone 1000 BTC.
I can sign a contract today I owe you 1000 BTC without having ANY coins. if I was a bank and those deposits were in a checking account under your name, that would be considered part of the money supply.