His son isn't running the company. The company has a CEO, who isn't a member of the Buffet family.

If you want to split hairs as to what the responsibility of the Chairman of the Board of Directors does, you win.

IDK, maybe I'm a mushbrain but it seems like if someone said they're the chairman of the board, and you told them to their face "well it's not like you run the company..." they'd finish their drink and go talk to someone else for the rest of the night.