HeightLerp + MatLayerBlendWithDisplacement

¿What is the purpouse of the output “Displacement” from MatLayerBlendWithDisplacement?
After breaking the attributes seems to do same as WorldDisplacement> WorldDisplacement

¿Crack Free Displacement?
Yesterday with a landscape break by holes caused by the displace I clicked it ON and fixed them.
Then I cheked backward to OFF and the fix continued without problem.
I dont know why sometimes there are hole cracks in the landscape and other times nothing.

With the HeightLerp + MatLayerBlendWithDisplacement I need the BASE floor layer not to move up. But when I use the displace both layers moves up and the floor layer do not maintain the position.
¿Is there a way?