I like what you've said but I think Satoshi was a group. You're correct in 2009 bitcoin didn't have value but they still could've shared private keys because sooner or later 1 million of 21 million bitcoin's got to have some effect. It's negligent if Satoshi didn't find ways to move the bitcoin years after Satoshi's absence.
If the bitcoin haven't moved from Satoshi's wallet there's a possibility the group behind Satoshi shared parts of private keys between them.
multisiig was not a thing in 2009-2010
there were no 'group' keys
secondly. satoshi was a single person with a single username
he talked and interacted and got help from other people. but they had their own names
like Hal. like Sirius
hal and sirius did not work physically in same room, building, neighbourhood as satoshi. they interacted over the internet
they were independant of each other not thinking of themselves as a 'group'
sats and btc had no value in 2009-2010 there was no reason to share keys. the mindset back then was not save for retirement. the keys had no value and of no importance.
also sharing keys then defeats the whole security model of bitcoin. the idea is to move value by spending value on bitcoin not handing the private keys to people
EG first transaction to hal. was done onchain by spending 10btc. not by giving hal a private key and then him moving them at his leisure