Thank you for the additional information, I can see why you would want want OpenSL to be the default and I am interested to see what results you get from AAudio with devices reporting the FEATURE_AUDIO_PRO flag.
The only place I can find any official reference to OpenSL being depracted is in the Android Latency Blog, so it might not be official. In any case I have passed your suggestion of making OpenSL the default onto the Dev team.