I meant more that Apple's philosophy is a scaled down experience. They always talk about "getting rid of distractions". The thought of people doing several things as once, as in Sentry's mockup above, must seem foreign to them.
I see your point, but I would go as far to say that the philosophy with the iPad is an incomplete one. Compared to iOS on a 3.5" the OS is more or less the exact same as far as functionality goes. That's definitely missed opportunity.
If you remember how apple revealed it, the iPad was supposed to be at the crossroads between an iPhone and a MacBook, yet that's only true in form factor. I remember everyone expecting OS X on it or some kind of iOS hybrid, but instead it was just the same os on mobile, stretched.
And I doubt the idea is foreign to them, anyone who's ever used a desktop OS in their lives (90% of iPad users?) have probably multitasked before in some fashion. Hell, on a screen just an inch or two bigger than the iPad, even (MacBook Air). Also, that's still quite a scaled down experience as it is. The access method is intentionally subtle and non convoluted with other iOS elements (like the switcher).
As Liu said, as long as it's a simple solution that offers something they think their user base will benefit from, while not interfering with what already exists, there's nothing they won't do.