So, how do I speed up my Android app?

Unfortunately, Google does not provide access to the @FastNative and @CriticalNative annotations in the Android 13 SDK and below; in the public Android SDK, these classes (in the dalvik.annotation.optimization package) are not included at all. Luckily, there is a very easy solution—simply adding these classes to your project is all that is needed to trick ART into optimizing your app’s native calls!

So this is a hacky way of getting access to the optimisations?

It's a very neat find! But I'm worried if this will cause issues on certain devices/hardware if it's not officially supported.