But, Satoshi's public keys are known. Back in 2009, the coinbase transaction was P2PK, not P2PKH. So, they couldn't mine to a burning-looking address. They had to firstly mine them and then send them to such address.
Why the two steps? If Satoshi really would he could just mine to a public key and then raise the value of that by 1. So something like:
Block 0, payout to:
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001
Block 1, payout to:
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002
Block 2, payout to:
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000003
etc..
In that case the blocks would have been clearly marked and they would be unspendable because they are like the P2PK-version of a burner address since there is no way the private key is known matching those public keys.
So if Satoshoi's goal was to clearly mark the blocks he mined he could have used such a solution instead of messing around with the LSB of a nonce. But like I said before, Satoshi really cared about privacy so there is now way he intentionally marked the blocks he mined. I believe it's probably the other way around, his plan was to never spent the coins he mined but he wouldn't clearly mark them as unspendable since this would give away those coins were mined by him in the first place.