Not an expert either but number of cycles is not everything, transistors that transition use up more energy than those who remain in the same state. As such it

Not an expert either but number of cycles is not everything, transistors that transition use up more energy than those who remain in the same state. As such it's possible that 0x00000000 + 1 uses up significantly less energy than 0xffffffff + 1, just because of all the bit flips. That's just a guess though.