Perhaps constantly seeing and feeling the read and unread pages of the book reinforces the sense of when things happened in the story.

I strongly suspect you're right. I know that before I could 'grep' digital text, when I remembered something I read in a book, I'd have a rough idea of its page-depth and position on page (in addition to general context) which aided in a visual-scan to re-locate.

Perhaps an e-book interface with stronger indicators of progress could cure the discrepancy. (One idea: shift the entire page slightly inside imbalanced margins based on how deep in the book you are.) Or perhaps people who have only ever read e-books wouldn't be as dependent on pending-pages-physicality.

Or maybe future Kindles could actually become flatter as you progress through the story, via some sort of deflation mechanism.

There's nothing more annoying than remembering only that a certain quote you'd like to reference was on the bottom of a left-hand page of a book you finished last week!

Why didn't they mention ebook beats on "objects"

For some reason, they chose a Kindle DX which is not book-like at all, and would have substantially larger pages. Why wouldn't they have just used normal Kindles?

People who read a lot like high word densities. I find the small size of the standard Kindle annoying. The DX is fairly close to the size of a hardback textbook.

I'm sad that it's still so expensive, though, especially since it has that dirty gray look compared to the newer e-ink readers.

Based on my experience, I read e-books faster than paper books, which can make timelines a bit fuzzy when remembering.