If bunches of apples are left to their own devices, this is what can happen. Then, as they grow, they are crowded and obviously the tree has more fruit and can't deliver the nutrients the fruit require, and they consequently don't grow to an acceptable size. So each bunch of Gala apples is thinned to one (theoretically, as it's hard to train new people to remove most of the apples on the tree), and Sundowners are treated the same way. However, Pink Lady's in our environment tend to thin themselves, so they are left to do their own thing.
See below a picture of a tree after thinning, and notice the apples on the ground.
Also note the white powder on this tree. This is a product which we use to help reflect the sunlight and thus reduce sunburn in our apples. It is a natural clay product and we apply it each week to ensure the apples are covered as they grow.