It is, but why comment on sweetness if you have an "expected" taste from wine, whether it's grape or blueberries? Anyone who orders wine should be expecting it

It is, but why comment on sweetness if you have an "expected" taste from wine, whether it's grape or blueberries? Anyone who orders wine should be expecting it to be mostly sour (or dry to use wine terminology), unless it's explicitly labeled as a dessert or fortified wine. My hypothesis is that it's because they like the sweeter taste, and are unpleasantly surprised when the taste is very similar to the sour one of grape wine; when they were expecting something more like blueberry juice with an alcoholic kick. It's possible that my hypothesis is overreaching. Testing it would involve a blind test with regular and sweet blueberry wines.