I agree that explains how 12 relays could be deployed...but I don't see how it performs any different/better than your 8-relay method. The force-OFF switch in your method could be placed on the output relays (red X) and these switches would not need to be heavy-duty 10-Amp (or whatever) switches.
Plus, with the presumed 12-relay method, the nominal condition is all 12-relays are "active". And for heavy-duty relays which might draw 1 Watt per coil... that's 12 Watts of overhead. OK, 12 Watts does not break the bank. But all 12 relays carry the full load current per block...whereas with your 8-relay method only half of the relays carry full block power so lower capacity relays can be used for the sense function so less expensive relays could be used.
In the absence of further information, I vote for your 8-relay method which AFAIK meets the known requirements.
