What use for the thin, folded, two-side protector that was boxed with my iPhone XR?
Your "Apple Protector" is just a cheap piece of plastic made for disposal:
it's just there so you can remove it and view your new phone in its glory without fingerprints.
Apply the real (Belkin) protector immediately for protection.

Proof: the Apple Protector usually doesn't have openings for the earspeaker part.