Another thing is that Satoshi included a hidden message referencing The Times newspaper on the genesis block's coinbase timestamp parameter (The Times 03/Jan/2009 Chancellor on brink of second bailout for banks) and never mentioned it.
That message was put in there to give prove no mining was done before that date. So it was there for a purpose. Since Satoshi was very strict about privacy it wouldn't make sense he intentionally created a way to distinguish blocks mined by himself.
I never hear/don't remember about this, can you show relevant source about it?
... and it is unlikely that the remainder will ever be spent, although the question remains why Satoshi didn’t simply burn them in this case.
Take note it's not impossible Satoshi get random 256-bit binary
as public key and use it to generate burn address.