If your phone came with a screen protector, it did NOT come with one preinstalled by Apple. Apple has NEVER EVER preinstalled screen protectors on iPhone. EVER EVER EVER.
If I were you, I'd be more concerned about the battery in your phone. It says it likely wasn't touched before you got it and you simply bought a used iPhone which came from the previous owner who had installed a screen protector. There was no reason you couldn't remove the screen protector if you wanted to. Seeing a photo of another 13 Pro Max isn't going to offer you anything.
Simple truth is you bought a used iPhone. It's going to need a new battery in a few months. If you're OK with that, then just use and enjoy the phone until the battery health dips to 80%, then pay Apple $89 to replace the battery.