When cooking in bulk to such a degree as these recipes represent, you can't reduce the base sauce down as far as you can in a small pan containing only a portion or two. The amount of base Bob is adding might seem low to you, but I bet it is used to provide enough liquid to achieve the right consistency and after cooking out for the requisite time, it will not need topping up with more base as the water lost through evaporation will be much lower (proportionally) than for a smaller batch.
Bulk cooking is a little different like that, and if you wanted to get technical you could calculate the amount of heat energy needed to evaporate 200ml of water from 350ml of base and multiply that energy by 60 to see if it seems reasonable that a commercial cooking range could supply it, or whether Dungeness B has more chance of achieving the feat.