It's not an unreasonable fear, they've been doing that using traditional breeding techniques forever, at the expense of world health. Genetic engineering only gives them more power to abuse. And I'd like to be able to avoid those foods.
Similarly with grains, the elevators pay based on weight. I've always worried we might accidentally select for really heavy but useless crops. Similar to the Swedish farmer who replanted only the biggest kernels of wheat. And got a crop that produced single giant kernels of wheat.
And none of that should be surprising, because no one tastes these things before they buy them. They judge based on appearance entirely.
Sweet corn is much sweeter than traditional corn because it was traditionally bred to be that way. But regular corn, and other staple crops like rice, wheat, etc, are just sold based on weight. They also do moisture tests and subtract the weight of the water content. But as far as I know they don't measure or care about sugar content.