as an example, there is a sugar warning on orange juice and no sugar warning on a chocolate bar i bought the other day after a blood test. the reason is that the test doesn't appear to differentiate between natural and added sugar. the 3 L container of orange juice would perhaps have more total sugar than the 100 g chocolate bar, but that is of no relevance to anybody's health. no health body has ever suggested orange juice is going to give you diabetes or make you fat. it's one of the most healthy substance available, and it's glycemic index is quite low.
this system would tell you to eat a mars bar instead of a grapefruit.