If we ignore the "EZ-play" books for a second and look at the many professional SATB-type scores I've purchased, augmented chords are still pretty rare. So having a two-note shortcut for them isn't very useful. But C/E (or generically, root with third in the bass) comes up a lot in pop, singer-songwriter type stuff as part of a descending bassline. When you play E below C on a Roland with Bass Inversion activated, it gives my preferred C/E. Unlike Korg, even with Bass Inversion off, Roland doesn't have a two-note shortcut for augmented chords. You just have to play all three notes, or substitute a major chord.

Dave I'm not 100% sure what you mean about the 5th. One thing that CASIO got very right: playing 1+5 gives you an open fifth "power chord," which can be very important to an authentic cover of the song. On Roland and Korg, playing C+G in intelligent mode gives you C major, which is a huge wasted opportunity. (Because you can easily get C major by just playing C by itself!) There's no good or easy way to get an open fifth on Roland or Korg without switching to a much more difficult chord recognition mode.