It's all well and good to say such and such is the reason, but that's not what the license actually says.

What's to stop a tool developer producing an Objective C library and compiler that can target both iPhone and Android? The original source would still be in Objective C. If it was developed specifically for the iPhone, and only later for Android, it wouldn't be a compatibility layer - only the Android port would count as the compatibility layer, with the iPhone original being the native one.