Just like coding is a technical skill to make a software product, the ability to make sushi is a technical skill to make the product he sells called sushi.
So to my mind your story illustrates the fact that Andrew's definition is not wrong.
What you can argue though, is that possessing the skill to make the product one is growth hacking on should not be essential in order to be a growth hacker, though having that skill would be helpful. After-all you can buy an off the shelf software or hire contractors just like the sushi guy can outsource or buy from other restaurants without making the sushi himself.
So to my mind your story illustrates the fact that Andrew's definition is not wrong.
What you can argue though, is that possessing the skill to make the product one is growth hacking on should not be essential in order to be a growth hacker, though having that skill would be helpful. After-all you can buy an off the shelf software or hire contractors just like the sushi guy can outsource or buy from other restaurants without making the sushi himself.