It was bad drafting. The answer to which was not another comma, but to separate what was written as one list into two lists.
The original was:
The canning, processing, preserving, freezing, drying, marketing, storing, packing for shipment or distribution of:
(1) Agricultural produce;
(2) Meat and fish products; and
(3) Perishable foods.
Better drafting would be:
The canning, processing, preserving, freezing, drying, marketing, storing or packing, for shipment or distribution, of:
(1) Agricultural produce;
(2) Meat and fish products; and
(3) Perishable foods.
The Oxford comma is still rubbish.