Of course the idea behind this could be that 120 needs bigger tank for the same number of rolls, and the number of process runs with the same chemicals cannot be increased infinitely because of oxidation and contamination that always happens when the used chemicals are reused later. But still, max four process runs are recommended for 120, and for example 135-12 five process runs is possible, so this can't still be the only reason.
"8 rolls per process" for 5 liters is very low. In our Jobo rotary processing, there's 300 ml of processing solution in a tank accepting 120 (and even 220) films, that is 1/17th of 5 liters, and means that only a half 120 roll could be processed at a time if I followed these instructions. It's just silly. These instructions don't make a sense at all. Good thing that they are not a law that must be followed . I think I know how to use the kit after all.