Person A deposits 100 BTC. The bank A loans 90 BTC to person B.
Person B deposits 90 BTC. The bank B loans 81 BTC to person C.
Person C deposits 81 BTC. The bank C loans 72 BTC to person D.
Person D deposits 72 BTC. ...
Total apparent number of bitcoins in the system: 1000
That's classic fractional reserve banking and it works with dollars, bitcoins, gold, or seashells.
I think he's saying that the "apparent" number of BTC isn't the same as the "real" number of BTC because BTC isn't a claimcheck on something unprintable, but is itself unprintable. I.e, the fractional reserve isn't built into the currency itself. Sure, I can deposit 100 BTC and the bank loan 90 BTC of it out, but I can't spend that 100 BTC unless the 90 BTC is repaid, or unless someone else deposited another 90 BTC and I requested my withdraw before the bank could lend it out.
Putting it in terms of the terms on the fed's balancesheet...
"Currency in circulation" can't increase
however, you are correct in saying that M2 can increase.