Learning to code is difficult.
Making board games isn't going to make it easier, you learn by doing.
I think what bothers me is that your advice is fixated on becoming a game designer. It's also a small part in the sense that you will have one guy doing it in a staff of 50. It's also arguably the hardest job to get and you need A LOT more than just having built a board game or two to get the job.
By using unity, he will touch on a lot of stuff and have a chance to find out what he likes. Building board games is only oriented to the game design part and won't really get him anywhere.
Not trying to be a dick here but bad advice imo.
I thought space travel was just around the corner until I was like 22 :(
Musk gave me hope when he sent a car to mars and then he spent the next decade either fucking democracy or fucking children.