I carried a couple of technical types from one of the radar manufacturers a couple of years ago. They were investigating that with the radar in auto, why CBs did not show up that well whilst flying over the Pacific. They came to the conclusion that the radars were calibrated for North American CBs which are apparently wetter.
Perhaps I'm just a luddite because I still use manual with the appropriate tilt/gain for the selected range................ it works well for me!