I think the puzzle creator should reveal the public keys for all the keys bigger than 120bit except 124, 134, 144, 154, this will make the challenge reflect the true strength of bitcoin security.
I'm not sure if a gold hoarding dragon is interested to risk more than what is already at risk. Lol.
But seriously if he wants to keep the coins there forever and not touch them, it would be better to move them to exposed public keys, because address brute force is practically pointless, unless he intends to wait and see what happens to technology 40 years from now, so practically unexposed keys above 80 bits serving no purpose, while as you said it, moving those coins to public keys would increase the incentive for new bloods joining this challenge.
I'm guessing he has either left the community "again" like in 2010, or he doesn't care about anything other than his fortune, as per usual.
We only live once, if we don't jump we'll never find out, that's why they call it leap of faith. You only find out after jumping.😉