What do you mean no? This is a widely known and commonly used approach. Citric acid, salt and bitter compounds are some of the most prevalent options. This isn't even remotely close to a controversial opinion.
I mean no. All those compounds are used for flavor. They aren't used to mask sweetness.
Manufacturers design foods to taste good, not for some secondary effect of sugar in the stomach.
The idea that the sweetness would be "unbearable in your mouth" is just plain silly. People suck on lollipops which are pure sugar -- are those "unbearably" sweet? What you're saying doesn't hold up to even the slightest scrutiny.
Manufacturers aren't going to waste money on additional sugar and then try to undo the taste with other ingredients. That's not a thing.
