I’m not entirely sure either, but I have a theory. Most flavors are not from just one chemical, the perception of a single flavor (apple, cherry, tomato…) is really a combination of many chemicals. Although it is common for one chemical to dominate the flavor profile if tasted alone something would taste “off” or “missing”. So, when natural and artificial flavors are used in combination for a single candy I would guess that they use the natural to get all the different chemicals, and the artificial to boost the main flavor component. This is just a guess, but it’s a chemically well-informed one!