This may be one of the most important features of the new iPhones

Apple has added a new feature with its iOS 13.1 software update that will prevent iPhone users to put non-genuine displays. Apple has detailed a support document revealing that it will notify the iPhone users if Apple has not been able “to verify this iPhone has a genuine Apple display.” Notably, this feature has been enabled only for the 2019 iPhones — iPhone 11, iPhone 11 Pro and iPhone 11 Pro Max.
Apple says that if an iPhone user has to replace the display of their device and the new display happens to be a fake, then they will see a notification on the Lock screen for the first 4 days that they use their device. The same will also be present in the Settings app for 15 days. After that period, the same can be seen in the notification by going to Settings > General > About.