I don't know if this is related to #270, but the command seat retains an inventory space separate that of the Kerbal themselves. It doesn't look intentional, but is it possible that command seats are supposed to have a separate inventory and the action just has the wrong tooltip?

("Inventory" in Bill's PAW opens the inventory panel on the top-left. "Bill's Inventory" in the command seat's PAW opens the inventory panel on the bottom-left.)