I can't find those titles on the iBookstore. The first Sesame title I came across in iBookstore "Elmo Says Achoo!" was not created in IBA and has no row of thumbnails. It reads like a traditional picture book. The ones you point out are an app in iTunes and not what we are doing here.
It's not that your kids notice or care that the thumbnails are there in that app, it's that I care. I am the creator and producer of my content and I want to present it in the way that I want to. I have spent at least a hundred hours filming puppets, editing, sound work, taking stills, writing text for this video eBook and even more to learn IBA.
As I said, I will slog thru this book to present in iBookstore under the layout limitations in IBA and simply move on to Pages if there is no update to correct/not include this flaw on the other books in the series. Love the interactiveness with widgets , adding video, etc but Apple should give us the option of having those thumbnails or not.
Also, you are right about children not caring about those thumbnails. I'd be willing to bet your kids never once said "Why aren't there thumbnails running along the bottom of the book?" when you were reading to them in the past. Children will accept just about anything you put in front of them as far as entertainment/reading goes. Will children's book authors with a hundred years of creating picture books at their back suddenly abandon their roots to a process that takes creativity away from them? I dunno. I don't see a lot of children's books in the iBookstore.
So, no crow on this one.