The main issue here is that as Mr. Keys observes, most of the power of the unit goes towards signal processing.

These are stomp boxes, not PCs or rack units with gigaHertz processors.

If you send it 128 MIDI messages back to back, it will process each one in turn, some of them causing display updates or other significant work, and it will not be instant. Obviously it has various tricks to try and speed things up, but there are limits.