"There is an apparently new iOS 18 security feature that reboots iPhones that haven’t been unlocked in a few days, frustrating police by making it harder to break into suspects’ iPhones
…
Apple added “inactivity reboot” code in iOS 18.1 that triggers iPhones to restart after they’ve been locked for four days"
Android is already disabling fingerprint reader every 72 hours. So what’s the difference?
The encryption key of the device storage is kept in memory while in AFU state for practical reasons, you don’t want to wait for the encryption key to be generated everytime you unlock the device, then wait for apps to restart and sync their data.
A reboot will discard that key from memory and return the phone back in BFU state, making it much more difficult to extract data from a device.
https://blogs.dsu.edu/digforce/2023/08/23/bfu-and-afu-lock-states/