Because as I wrote above, GPU frequency/voltage for P1-P7 is read from modded BIOS and used. But for memory only P1 frequency was set, but voltage still is default 1000mV instead of flashed value. I don't know why.
Have a look at bios mod threads, if gpu vcore is too high, then memory voltage stays at 1 V whatever value you set. I don't remember the exact rule