I checked the transactions and it seems the last time he sent any ETH from that address was back in May 2019, so its very strange where he has been away so long. Another reason could be that maybe he is just hodling these coins and wants to sell when >$1000 or so.

However he sold the coins back in May 2019 because its when it recovered from the $80 low. It was $80 back in Dec 2018 and in May it went to $250. Then a few weeks later it went even higher. And last month ETH went even higher than that at almost $500. So it doesn't make sense why he didn't sell.

100 ETH isn't really that much money so who knows. That address might be one of his "chump change" accounts and he is just letting it sit.