Lighter wheels & tires do have a very small additional benefit due to the lower amount of power required to rotate them (true of all rotating components), but this is not due to their classification as unsprung weight.
The unsprung vs. sprung weight percentage greatly affects wheel control, but its importance is almost entirely limited to un-even surfaces, or conditions where the attitude of the vehicle changes (such as through G forces). This is most important in off-road and pavement road racing, somewhat less important in dirt track, and has almost no value in drag racing. As the importance of suspension travel for proper wheel control diminishes, the value of reducing the unsprung proportion of the total car weight is lessened, and becomes zero if the suspension travel is zero.
Cars requiring precise control of wheel movement, where a low percentage of unsprung weight is an advantage, will have faster lap times and higher top speeds, not because unsprung weight reduction improves acceleration or top speed, but because traction is improved.