Samsung dropped S-Pen support for the Fold 7 because nobody used it, not because it scratched the screen.The main issue will be the flexible inner screen. Apple could have special tips for the Apple Pencil but I assume they would not risk someone using the wrong tip and damaging the screen
Given the iBook will just be iPadOS on the inside there are many, many more compelling use cases for Apple to put in Pencil support because it will just run the iPad version of app binaries on the internal display.