Yes, I have pointed this out before. I found it extremely confusing at first.If you go to the FM Radio screen then the station list icon looks like this. (Icon_1.jpg)
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Go to the USB screen and the song list icon looks like this. (Icon_2.jpg)
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Where as folder list icon looks like this. (Icon_3.jpg)
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Consistency must be a word not understood by Mazda software designers.