What it is
The legal term for "we won't tell you." Can cover dozens of compounds under one phrase. If it were fruit, the label would proudly say fruit.
Why your biology objects
"Natural" only means the starting molecule came from a plant or animal — it can still be heavily processed and bundled with solvents and carriers that never appear on the label. The point is engineered palatability that overrides your satiety signals, from an undisclosed source.