This is an incorrect statement. I’ve been doing this a very long time. When you click “Install Later” there is no final warning if the package is already downloaded to phone. It’s possible we’re just using different terminology. I would agree that there’s no “auto“ install in the sense that you have no options. But the install later option on iOS 10 and iOS 11 replaced the install tonight option from earlier firmware. There is no other warning you get after clicking install later.