maybe they can bitch about their weak engine this way and Renault can live with it knowing they need a lot of HP to move the water..
Seriously ..I think this is a trend... errm.. F1 engines have engine driven waterpumps still?
i think most teams use transverse flow radiators now so a long radiator will feature a lot of short tubes...leading to a not very good flow situation at the exit of the inlet pipe as well as the outlet pipe leading back to the engine on both radiator connections you would have a very severe change in crossection leading to losses -plus the flow speed in the (core)tubes will be slow .Having multiple pass radiators will help the transition from tube to radiator core tubes and of course will elongate the cooling path for the fluid keeping the speed up -without resorting to insane water pump speeds.