It's supposed to do that. The voltages help to make the jump from no load to load less of a power jump for the processor. Let's say the proc is recieving 1.31V, but when load is placed on the processor, there is a small amount(not noticeable to human's) where the processor would take in the voltage and since this isn't recognized by the system until after it happens then voltage is pumped through to the processor( this would be a drop in voltage until the system can compensate).
Then there is the other way: load to idle. A smaller voltage(1.25V) allows the system to stop supplying voltage to the processor when it stops using the voltage is has(thus a spike in voltage occurs).
I hope this isn't too confusing, I'm usually bad at explaining ideas even if I know them well