The definition and abbreviation for Potentially Hazardous Food (Time/Temperature Control for Safety Food) or PHF/TCS should be modified to drop the reference to potentially hazardous food and PHF.
Yes, as a treat apples are fine for chickens. Some will say it is best not to feed them too many apples as the seed of an apple has a small amount of arsenic in it.
Only feed your chickens that which is still considered edible by humans, don't feed anything spoiled, moldy, oily, salty or unidentifiable. Lettuce / Kale. Any leafy greens, spinach collards, chickweed included. A big treat, depending on how much other greenery they have access to.