It might, but unfortunately, you can't build a library with it. It only transforms whole apps. Apportable was investigated in the first part here http://www.skyscanner.net/blogs/developing-mobile-cross-plat...
The C++ ABI is unstable. You can't effectively deploy 3rd party libraries with that either.
Android ships with multiple versions of the compiler, each one of those are incompatible with each other's standard library. On top of that, Android ships multiple C++ standard libraries for each compiler, all of which are not-interoperable either. Then Android updates the compiler with each NDK drop introducing more potential incompatibilities.
The end result is you can't deploy prebuilt C++ libraries (a prickly issue for commercial/proprietary code) unless you can force users to use your exact toolchain. But library writers usually can't fairly dictate those terms, especially if the users want intermix libraries from other sources which may use a different toolchain.
You are right though. Those libraries will link Apportable's extended/improved libc (called libv) and libc++ and would require distributing more parts of the platform (it can get a little hairy there). It is also true that the out of the box experience is one that is meant for just apps but it's built on a layer cake and at a lower level you can use it to compile libraries. This is how it builds dependencies in your Xcode project today.