My 2c.
As some have stated, 4 in and 4 out, means 8 hoses into the rear of the truck.
Have fun reaching over to which ever switches and dials you need to get to. Not to mention jumping over the lines to go to either side of the truck. - That is one of the only real design faults, or more should I say, designer points, that I disagree with.
Sure, you can argue all day that you should be able to use the pump regardless, and sure, I agree. But splitting lines to the side makes it easier. Fact. You can send a delivery off either side, while keeping the rear of the appliance less cluttered. - Has its pro's and cons sure. Everything does! But I have to agree that having all 4 in and out from the rear of the truck will get messy.