I understand that this doesn't change the point you're trying to make, but the Block 0 coins are not spendable, regardless of whether the private key is available or not.  Just wanted to point this out for anyone that might think that they are.

Your statement would be more accurate if you stated:
"If Satoshi signed a message with the Block 1 output address, that 'they won't move the 1.1 million coins', even then these coins were moveable."