The iPhone 15 pro is mostly aluminum. There is about a 1mm thick band of titanium around an aluminum frame.

https://www.apple.com/newsroom/2023/09/apple-unveils-iphone-... https://www.youtube.com/watch?v=S_W73ouKtjU&t=605s

And that makes perfect sense.

Thick walls on the iPhone are what are going to prevent X Y area which I suspect they need more than thickness.

Seems like marketing to me. They got rid of the stainless steel frame from previous models, switched back to aluminum, then added a pointless band of titanium so they could say Titanium in their marketing.