And you can absolutely get your iPhone battery replaced.

Apple literally refused my request to pay for a battery replacement and claimed my battery and performance issues was due to a dent (flake of glass missing) in the screen.

Maybe you misunderstood them - for me they just flat out refused to replace the battery due to a minor dent - primarily because they alleged their machine can’t operate on the damage iPhone anymore. Which while a dick move is at least plausible.

Maybe. But the way I remember it is that it was clear from their side that replacing the battery would not resolve my performance issues even though I wanted to replace it to fix the random shutdowns and quickly worsening battery life.

In any case, it looks like an even greater flaw in Apple's design process if they are unable to properly service a phone with a dent in the screen. It should not be unheard of, especially since they seem to keep on highlighting better and more resistant glass every year or so.

How would you know to do that. The company went out of their way to lie to their users specifically so they couldn't know to replace the battery.

It is quite strange that you give this reply as they are having to pay out exactly because they wanted their customers to think their phone wasn't up to the task anymore instead of their battery dying.