Operating system: Windows 7x64 pro
Graphics card: Radeon Pro Duo Polaris
Broken: All versions plus 2.80 RC2
Short description of error
Objects with micro displacement have strange material previews. Scale is wrong. Not sure if this is a bug. But it seems if we had a scene scale setting to override/ manipulate the material preview scale, then we could get the materials to look correct for micro displaced materials.
Exact steps for others to reproduce the error
Subdivide cube and micro displacement material. Scene scale to one. I use Imperial units. Add subdivision modifier as you would for micro displacement material. See attached image for reference as to what i am talking about.
Based on the default startup or an attached .blend file (as simple as possible).