Come to think of it, does it do the same with Time Spy? I'd expect Time Spy to be far better at using 4-8 cores.
(Ryzen also supposedly learns from what it's been doing or sommat so I'd have to poke around myself.)
Performance difference with Timespy was negligible between the different power profiles. I guess the theory is right now that in power saver, core parking prevents the CPU from cross shipping threads across the CCX.
Ryzen 7 1800X at 3.9 - Corsair H60i - GA AB350 Gaming - 32GB DDR4 2666 at 14,14,14,34 - Gaming X GTX 1080 - 250GB WD Blue SSD - 2TB Toshiba 7200rpm HDD