I can't answer your question, about why use short rods out the back .... but, you must be using some of that "fuzzy math" for your rod distribution
The law says you can only 'fish' with a max of "THREE" rods per person ... and that means that each person must only be tending a max of three rods ... NOT that the number of rods vs the number of persons fishing should divide out to three apiece
... cp