From memory.  Unconfirmed by re-visiting.

What I think you’re seeing is that the MicroPitch is preserving the current values in its buffer (Preset “0”), and restoring that state back again on power-up.  Not really the same as an auto-save, because it is temporary.  I think you’ll find if you switch to another preset, than back to the original, the output volume will revert to its saved position.