Why there is a passcode on my iOS update?
Why a pass code is being ask now to update my iOS
iPhone 13, iOS 16
That has been a requirement for my device updates for as long as I can remember. Also see the following from Update your iPhone or iPad - Apple Support
5 - Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now. If you don't know your passcode, learn what to do.