The Apple Books version wasn't just a static animation—you could partially flip the page, flip it back, make just the corner flip up a little then push it back in place, et c., all with smooth and responsive enough operation that it was close-enough to feeling like a real, physical thing. The "back" of the page, as it flipped, showed the text from the front as if it were showing through thin paper, it wasn't just blank. Lots of apps have page flip animations but most of them are both non-interactive and bad. Apple's was interactive and good. Dunno if Kindle's is as good—I used it long ago and my recollection was a slow, ugly, non-interactive page flip animation, but it may have changed since then.

Kindle's animation is pretty good, and I did that fidgeting thing with it all the time. I've never experienced the stuttering on Android that the OP has on iOS. It also shows the text bleeding through the back side of the page.

But the animation is disabled by default and lately I've stuck with the regular sliding animation because it's faster and much less obtrusive. It also lets you start turning the page as you're reading the last line.

I disagree that something like this could have been an oversight. A designer spent time coming up with the new animation, it was approved by somebody in a project management role, and engineers had to spend time implementing the new feature.

Apple has an intense culture of dogfooding, so it would surprise me very much if someone in a leadership position didn't experience the new page-flipping animation, much less explicitly approve its design.

> fell out of QA testing

That’s not really a change you miss if you do any QA of that app at all. And if it was missed that’s even worse for Apple than if it was a conscious choice.

I’m trying to imagine QA testing that doesn’t ever actually turn the page

My shill for Apple here is that the simple sliding animation is much better. I never liked that book animation. It felt heavy and distracting and out of place like most skeuomorphism.

It wasn't just skeuomorphic, it had a functional component. It helped you keep your place and maintain context as you turned the page, just as you'd do with your finger while reading a real book.

No one has ever designed a physical book that works anything like the new page-turning approach, and you have to believe there's a reason for that.

It's very clearly a choice and not a bug

But what I could imagine is that it fell out of product oversight and an engineer just came along and said "well that's a really complicated piece of code, I don't want to maintain that, I'll replace it with something simple", and nobody pushed back because this isn't a high-priority feature any more