It's not saying marijuana makes you smarter, it's saying that something 100x stronger than marijuana can stimulate brain growth - and that, while this brain growth probably doesn't contribute to intelligence, it may indeed have anti-depressant and anti-anxiety effects.
I have been a computer programmer most of my working life 44+ years. Yes it makes me smarter.
In my drinking years I'd make sure I had simple stuff and cleanup to do the day after drinking. Not so with marijuana. A toke or two makes work more fun and thus you do a better job. Pot makes you smarter for sure...
I have a list a yard long where I did a superior job.
See "nobody shares knowledge better than this" that claim remains unchallenged after 2700+ responses
I take tests better high everytime.
I take better notes stoned everytime.
I concentrate easier when im high.
I argue better when I'm stoned.
I play video games better when Im stoned.
I even get better workouts when im stoned lol.