The problem with Expression select is that it does not take care of the actual pedal position, and as soon as we change by and Expression Select the instrument attached to a pedal, and as soon as we move it, the MCx interprets it as a real position for the new instrument. And sometime it is hard to manage this without a huge ‘bump’ in volume (when Exp manages volume) or whatever parameters it manages.
Korg has the same problem for the buttons on various of its synths I know, as the Opsix, Wavestate or Modwave.
But there is a global parameter which comes to give more facility to manage this, here is an extract of their documentation which explains their solution :
Morningstar MCxx are actually exclusively in the Basic Jump mode, implementing the Scale mode for Morningstar EXP pedals processing should bring a new level of usage.