The superintendent felt that interactive books were the future of education and content absorption.
They also Pearson to make the software. (i.e. they weren't just buying existing software). They could have commisioned software to be made on any platform, or even for it to have been cross platform.
Your use of the word "video game" for these titles I think means you haven't seen then.
I have seen some screenshots, and I see why you don't think they would be perform well in HTML5. They have video game level graphics. This is also why I pointed out unity as an example of a popular framework that targets all the platforms I mentioned (that you seemed doubtful of). Unity is marketed as a game engine, but you can make whatever apps you want that require performant graphics.
The web is more interactive than a book. That allowed for vastly more content and student led exploration.
I agree with this statement. I think interactive books would be very helpful in illustrating concepts in ways that a static medium can't. I was envisioning something like wikipedia with it's animations and maybe some added interactivity. I don't think you need to see a emmersive 3d world of an artists conception of ancient Rome to effectively learn.
Interactive books do the same thing. For example a science book my daughter has allows her to conduct the experiments associated with a concept in a simulator right after learning the concept. That helps retention and understanding.
I think this can be done much more cheaply than ipads and proprietary interactive textbooks of the sort you are describing. I think kids are capable of learning concepts with a lower production value. (i.e. the kind found in HTML5, like wikipedia).
1) There are more of them
This is irrelevant if you are commissioning your own.
2) On average they are better written.
debatable and see my point for #1
3) They can be more easily written because there are a limited number of platforms
Developers actually prefer android for development, but prefer iOS for profit potential.
4) There are better authoring tools.
Such as? Android apps are java which has a much bigger following than objective C or swift.
No they aren't. And the way you can tell they aren't is by looking at variables on usage. For example average phone application interaction is 30 seconds. Average tablet interaction is closer to 5 minutes. The fact they run the same OS doesn't matter the fact the glass is bigger does.
The fact that they run the same OS means that the time spent on developing "phone software" vs. "tablet software" is the same, because the same software runs on both. While you may feel subjectively that phones and tablets are very different, the people developing the apps that run on them are targeting both platforms simultaneously. It's crazy not to. In fact, now the trend is to target phone, tablet, and desktop browser simultaneously with things like google polymer, and phonegap, etc.
Developers don't like writing different software for phone, tablet, and desktop, windows, mac, linux, and all combinations, and now with modern tools, they really don't have to.
The only thing the size of the glass effects is which UI profile gets loaded. Properly designed software can easily abstract the functionality from the presentation, like in a MVC (model view controller) design.