TLDW: Their mandarin orange wine was a bit too bitter. Testing, unscientifically, if they can tell a difference. They can. They think it lowers the bitterness.
Interesting. I’m mainly a beer brewer (only my first cider recently) so I’ve not had a brew that’s “too bitter”, as with beer you WANT them to be bitter, usually. I’ve heard to add a pinch of salt to a pot of coffee.
Too long of a video.
Yeah upping one flavor will usually balance out others. It's why you'd never really cook something without salting it. At first they probably only salted enough for the variation you'd find in tap water if your friend brewed the same recipe.
I don't think a tablespoom of table salt in a five gallon brew is going to fix every error, but I can see why it might be worth trying for certain types of herbal/bitter/medicinal flavors you want to temper.
I probably would have tossed in some oak cubes and let it cellar for a month and tried it again, myself.