Those suffering with the cooling issue will be fully aware that it is largely down to their biking lifestyle, always accepting that good housekeeping makes sure the rad is kept scrupulously clean.
Take a K16 up a high mountain road, with slow hairpins & steep gradients & I suspect most will throw the red light & ask for a cool off half way up. Similarly, after a long blast at high speed, coming into a town & getting caught in traffic can create a similar scenario. It's the nature of the beast; after all, there is only 5mm between each cylinder, so no room for coolant between the pots. Clearly BMW optimised the size of the rad, so a twin fan set-up seems entirely logical to me; anything to dissipate heat & draw more airflow across the rad at low speed.