Its been a tough year for apples as the cold wet spring has been favorable for a wide variety of disease. Apple scab is among those. The tree is doing the best it can with what leaves it has. The older ones that are all scaby and now in the shade are not as useful as the newer leaves. The tree casts these older ones off to put more resources into the ones working better. Lots of trees, including apples, are shedding these leaves making it look a bit like fall. You can read about this disease here:
https://pnwhandbooks.org/plantdisease/host-disease/apple-malus-spp-scab