BB10 does NOT support Android/NDK --- and that is NEVER going to change. If your Android app has even a single line of c/c++ code, then it will not function in BB10's android runtime.
Plants vs Zombies and Cut the Rope have been available on the Playbook for a long time, so that's not a surprise --- and these have been ported from the iOS version to native BB10/Playbook.
If you see an app that requires a lot of CPU power (like a massive 3D game), then that BB10 app is a native BB10 app ported from iOS versions. Just look at the Galaxy on Fire 2 example that I cited above. Angry Birds on BB10, ported from iOS version.
Nobody creates an app just for the Android platform --- they don't get paid enough money. So they already have an iOS version of their app. And if there is even a single line of c/c++ code in their app, then it is much easier to port their iOS version to BB10 than to try to port their Android version to BB10.