If it was an error then that was a big error to make! I can't believe someone could just shoot over an entire fortune like that, its just wild to think of! Perhaps it was a flex or perhaps it was an accident we never really may know the truth. If it was meant to be on purpose certainly they have a boatload of bitcoin!
I don't think that it was an error. It was probably done on a purpose. Who knows that if this is just someone who has bought thousands of Bitcoin during the early days and want to thank satoshi for his contribution and he has done his part. But honestly, this is really a fortune of a lifetime that someone can easily drop off and forget about it. This guy/gal probably have a lot of money or BTC holdings and this isn't really a mistake but sort of token of appreciation and showing his/her gratitude to satoshi and bitcoin.
I think it is supposed to be a demonstration of ownership. The sender wants us to believe he has the private key to this address.
No, it wasn't a demonstration of ownership. Because if someone who owns that address, it's none other than satoshi himself. It is just a way to burn those BTCs forever.
Unless he moves the coins to another address, I don't believe him.
You don't have to believe nobody because it's the genesis block address and only satoshi is the one who's known to have access on it but we don't even know where he is or might be dead and unlikely to come back.