What you see is a simple plan with no double faces, checked and I'm sure.
This happens only when the mesh is at the local coordinate Z-0 height, if I move the mesh in edit mode, the flicker disappears
I'd just like to know if I'm wrong, or there is a problem. This with the "Brick texture" node does not happen, for example.
I'm using Blender 2.83 but it seems that even with 2.82 the problem is the same