I have been apparently unlucky with the texture that I chose to download and test. It is a metal PBR material but with a displacement texture that is mainly a light grey, with a few darker indents. To behave as I expected, it should be inverted (and the grey be black) and have a negative displacement. But probably was meant as a plated metal layer, slightly offset from the base geometry and it just goes crazy with the 10cm standard at the beginning.
In any case, because of this particular material, I found a strange display discrepancy.
I tested it with in a file with units in meters and displacement was automatically set to 0.1.
In the render Viewport mode it appears to be hovering approximately 0.1m above the plane, as expected.
However, in the raytracing viewport and in cycles rendering, it appears to hover only 0.01m above the plane.
I’m not sure this is a bug or a problem with my computer specs.
Out of curiosity, is there a logic to the 10cm, or is it to be sufficiently visible to force an adjustment?