Mysterious iphone xs camera lens crack

It depends on what it looks like. If it looks like a hairline fracture, they might consider that a point defect that eventually cracked under ordinary use. If it looks it was dropped then they won't. It's hard to describe, but I know it when I see it. Since the camera lens is fused to the case, pretty much the only "repair" is to replace the entire device. Not sure what the prices are in China, and Apple generally only offers replacement service for iPhones that were sold in the same country. Was your iPhone XS purchased in China through Apple or an authorized dealer. I mention that because I understand there's a pretty big grey market in China.

Do you have a photo? You can upload one here with the little symbol in the bar with the mountains.

Sorry. That’s not going to be covered under warranty. It looks like an impact crack. Not saying it necessarily is, but it’s got a spiderweb pattern and looks like small pieces fell from the crack.