Since when are "this" and "that" different, but "that" and "the" the same? That doesn't line up with Duolingo's lessons at all. It also makes no sense.
It's actualy fairly common to pair salt with sweet flavors. Peanuts and chocolate should have some amount of salt, and it's pretty popular to add sea salt to chocolate or even caramel. Ghirardelli's store at Disney Springs in Orlando has a sea salt caramel shake (last time I checked), and it's amazing. If you're used to eating cheap crap like Hershey's, you probably won't be familiar with it. lol