The AAP only includes stats from the 1200 publishers that submit sales figures to them. Lots of small publishers don't. In addition self published books on Amazon and others are also not included.
The AAP is, of course, aware of that but they're using their true statement to tell a lie; namely that ebooks aren't doing so well. Most people reading that statement won't realize that it doesn't really mean much.
There's the old story about the used car guy who took in a nice clean looking piece of junk that needed a lot of work but looked good. He called his grandmother and asked her to come by the lot and drive it to the grocery store, which she did. Later that day he sold the car to an unsuspecting couple explaining that the car had been driven by an elderly lady only to the grocery store. He didn't make a single untrue statement but he told a lie. That's exactly what the AAP is doing. There's a word for that. It's called "marketing".
Ebooks didn't do away with paper books overnight and that's partly because of agency pricing and partly due to marketing and partly because a lot of people just like paper books. Over time my guess is that ebooks will continue to do better, as they are now. I don't know that paper books will ever go away. I hope not. But at least for fiction they'll probably become the main way to buy books.
A waterproof Kindle kind of makes sense for a few people but for most people waterproofing has no real value. Most people read at home most of the time. People reading out and about mostly use phones. Reading in the tub is perfectly safe if you put your ereader in a baggy or in a waterproof case. The vast majority of readers will have no use whatever for waterproofing.
I have no use for waterproofing but if an ereader could be bought with or without it and waterproofing only raised the price a little I'd probably get it just to feel good about it. But not if it cost much more.
Barry