After seeing the duplication of resources in assets/META-INF folders, I investigated this further to find that there's a huge amount of unneeded leftover files left here that can *and should* be deleted for a release build.
For us, this is 11.5MB of a 42.5MB apk, down to 31MB after this clearout.
Basically, after deleting all files that match the regex,
assets/META-INF/AIR/extensions/[^/]+/META-INF/ANE/Android-ARM/(?!library.swf)
Leaves the apk in a perfect state, but a much more manageable / palatable size. This cleanout can be achieved after the building of the apk with aapt, from android-apktool - A tool for reverse engineering Android apk files - Google Project Hosting, with commands like,
aapt remove mygame.apk assets/META-INF/AIR/extensions/com.google.api.game/META-INF/ANE/Android-ARM/android-suppo rt-v4.jar
aapt remove mygame.apk assets/META-INF/AIR/extensions/com.google.api.game/META-INF/ANE/Android-ARM/appcompat_v7- res/abc_ic_voice_search_api_holo_light.png
This should *absolutely* be done automatically by the build process, because as I said this contributed to our app growing by a third of it's proper size.