You don't only need early adopters for such statement, you need early adopters who cared at all about they wallets through all of this time. Some people might have mine a lot of bitcoins in 2009 for fun and forget about them .
I guarantee this is the case. While 21 million will be mined, I'm sure a lot of those early coins are gone due to loss of the private key. How much we'll never know but I think it's more than people realize.