I don't understand what you mean by 'If macronutrient balance is the problem, then you still want to stop adding sugar'. We're talking about analysis of study methodology.

Do you mean that having too many carbs is detrimental to health? Because you can have an increased carbohydrate intake without increasing sugar consumption.

Let's assume the study is valid except that it failed to correct for macronutrient balance. It failed to replace sugar with pure carbs. Let's say this made a difference.

The result of the study changes, but it's not invalidated.

Sugar is still bad, but so are other carbs.

You still don't want products to add extra sugar.