I was on a plane that had to make a very sudden emergency landing. There was no time for items to be anything but tucked into the back of the seat or beside you, before we had to duck our heads down. The main injuries sustained were from people who hadn't done up their seat belts or from shock/panic. There were a few newspapers and magazines floating around, the odd book and small camera too.

So if there is another emergency and potentially free-floating items are flying through the air within the cabin, I'm far happier being hit in the head by a paperback novel, than I am an e-reader. Let alone a mobile or laptop.

What about a hardcover version of LoTR? The point is that this explanation is a retconing of the original reason for this rule, which has nothing to do with free-floating items in the cabin.

Did that emergency occur during the short window after takeoff and before landing when electronic devices are not allowed?