Problem is your argument falls apart when you are comparing it with Epub2 not Epub 3.
Apple iBook format pulls heavily from Epub 3 and from Apples history the lock out is blocking everyone but Apple products. It is not about a standard but about Apple lock in.
that's my point. if you ignore the "apple ecosystem" bias, it's a great tool for kids to learn. obviously apple's closed system approach works, or they wouldn't be the most valuable tech company in the world. i don't see microsoft, google, or any open linux company staking claim to that title. as tech nuts, yes we all like to poke and prod and fiddle. but for the basic user, especially kids who need something that isn't going to break or crash this is a good platform. the primary people that will be doing all this work will be doing on macs, for guess what...the ipad. sure apple has borrowed from many open standards and have also created many open standards. again, the argument shouldn't be about sticking to open standards, it should be about creating a fantastic product that helps students learn and excel...i mean numbers...owww wait, no i meant excel.