It looks to me like the "pre-oiled" label assumes that you're going to be freezing your pitas.
Food Service Direct, which sells frozen Kronos pitas, gives these instructions for preparing Kronos Frozen Original Flat Authentic Pita Bread:
Preparation instruction: Griddle (Thaw before use) -Pre-heat griddle to 350 degrees F -Lightly oil each side of pita -Heat each side for 30 seconds
Oiling a frozen pita (or adding oil to the pan) would certainly make it easier to defrost in a pan without burning.
I can't be sure that Kronos assumes, or suggests that you freeze your pitas, but I did find this Instacart listing for Kronos pre-oiled "gyro bread," which includes these instructions:
Warm in oven, microwave or on grill.
Keep frozen for maximum freshness.
I'd guess that those instructions come from the packaging, rather than from the seller.