The key phrase being "within the limitation of the platform." Apple's been pretty consistent in designing (and limiting) key developer APIs to be power efficient. And they're willing to ship later to achieve it. I mentioned WebKit. A more obvious example of this is their approach to multitasking. Android let apps do more or less whatever they wanted and they supported multitasking first. Apple waited until iOS 4, but the more structured and regulated set of APIs they came out with was much more battery friendly.
> I think the most charitable explanation possible is that Apple doesn't want any kind of "open with..." choice
Yet iOS 8 added a bunch of extension APIs.[1] You can literally open content in other apps via the system share dialog, including third party mapping and voip apps. The stated reasons for waiting until iOS 8 were that they needed to do a bunch of architectural work first.[2]
[1] https://developer.apple.com/library/content/documentation/Ge...
[2] http://www.imore.com/our-full-transcript-talk-show-wwdc-2016...