Other iOS SDK 16 < 15?

I got this email from apple about my latest build for testflight:

ITMS-90725: SDK Version Issue - This app was built with the iOS 16.0 SDK. All iOS apps submitted to the App Store must be built with the iOS 15 SDK or later, included in Xcode 13 or later.

But i'm pretty sure 16 is still greater than 15? It also has not complained about my other builds from that same day and I haven't updated xcode or anything.

Current plan is to just ignore it, but wanted to post it in case others have come across this. It doesnt seem to effect the availability of the build on testflight for testing, and the build can still be chosen when making a new version on app store connect for a new submission.

Unity 2020.3.38f1
Xcode 14.1