If you use a powerfractal for displacement then it's no problem to have the high or low color unchecked, or both.
But if you use a powerfractal as blendshader, the node which uses that powerfractal needs the powerfractals color for the mask.
So unchecking high-color then will not work then. Actually, I'm a bit surprised the strata will even show up if the blendshader is either not connected but activated or connected but without any color-input.
So my guess is that you have enabled the high color, but that the mask was not "strong" enough.
Anyhow, still nice work

Martin