It's probably easier to hear this effect in action than it is to describe it, so here are some audio snippets with annotations for clarification. It may also help to refer to the signal flow diagram from the manual, reproduced below for your convenience.
|Loomer Shift v2 audio signal flowshort|
Echo Shift Off
|Echo Shift disabled|
With Echo Shift switched off, the pitch shifter comes before the delay, and the delay feeds back into itself. The key point here is that incoming audio is pitch shifted only the once. The following audio file demonstrates a short orchestral stab shifted two semitones by the pitch shifter. You hear the dry signal first, followed by the shifted echoes.
Echo Shift On
|Echo Shift enabled|
With Echo Shift turned on, the pitch shifter is inserted into the delay feedback path. Each echo will be transposed again as it passes through the pitch shifter. The following audio file demonstrates the same orchestral stab, again shifted two semitones, but this time with Echo Shift on. You hear the dry signal first, followed by the shifted echoes. Notice that the first echo is transposed by two semitones, the second by four (two semitones from the first pass through the pitch shifter, another two from this pass), the third by six semitones, etc...
Diatonic Mode and Echo Shift
When Diatonic Mode is enabled, Echo Shift is automatically disabled. Diatonic mode requires a monophonic signal to track and harmonize, and so an Echo Shifted signal, effectively polyphonic due to the echoes feeding back, is not an appropriate source.