I was looking at my specific case were I have 8 zones in the front yard and 8 zones in the back yard. The front yard valves are all grouped next to each other. A single nine conductor cable runs from the valves to the controller. Same is true for the rear.
So I have two nine conductor cables going to the controller. One of the cables I had strip the casing further back so I could get a longer common wire. That common wire then had to run up to to the com terminal. Not a problem just did not look as pretty as it could have.
Using A typical 9 conductor cable as noted and three expansion boards (56 zones) would mean jamming 7 common wires into 2 com terminals, making a pigtail or adding remote com terminal block.
It’s an aesthetics request.