The purpose of the feature is to interpret the chord sheet using chords that are more common in the style that you have selected. The message is this:
I can duplicate the issue that VideoTrack has where the "complex chords" flash message happens if "Never" is selected in the Arrangement options. I don't think it's actually doing any reinterpretation but we will look into that further. You can avoid seeing the message by selecting "Never" in the "show message" drop down.