Apparently with this new thing that display RPPM on the item now on PTR it's clear that Rune Regen affects RPPM so UH gets 20% more than frost by default AND whenever RC proc is up it doubles the RPPM of the trinkets since it increases rune regen by 100%.
I was shocked when i saw this
Feather PPM for frost with BT = 0.72PPM
Feather PPM for UH with RC = 1.74PPM
Talisman of Rage PPM for frost with BT= 3.86PPM
Talisman of Rage PPM for UH with RC = 9.30PPM
And BTW this dk was reforged and gemmed for mastery so the PPM difference is even larger when you put the normal UH reforges.