"technically" you are correct, but in practice, keeping the intakes divided down the center for an extra couple of inches gives you a 1>2>8 intake runner, that has longer effective runner length. ....vs what would be in a 1>8 runner system. just like headers, there is 4>1 and 4>2>1. which works better? depends on the application. Technically if count the openings in a carb, you get 1>4>2>8 with a dual plane intake. (1 counted as the "common point" of air volume)
Also, longer runners make more torque. This rig is for towing.
Regardless playing with a throttle body will not change runner length. And longer runners make a more efficient engine down low, and shorter runners up high. So you would not want to lengthin your runner at higher RPM. Ideally it would gradually get shorter as RPM increases.