Sweet foods and Umami make a wine taste stronger and sour foods can make a wine taste milder. I have been mentioning this core rule for years. Tim Hanni developed this when he was at Beringer wines.
So it is only logical that they would use this as the basis to match wine and food.
You can get it from the "source" if you like, with more details that build on this principle. Click the title of this post and go to the wine and food pairing link on Beringer's site