Something to take note of is that zurb grid foundation has ballooned over the years, it used to be way more minimalistic and more modular than bootstrap. Bootstrap and foundation have stolen things from each other over the years and they are very similar today, but generally foundation styling is more subtle and I think that is what he is getting at. The ability to be unique with less effort than you would need using bootstrap.

Also Foundation has a superior grid layout system last time I checked, but dont quote me, I have not looked into bootstrap 4