[Edit: This side discussion has been split off from topic AMC Gremlin]
Investigating further...
Here is a comparison of displacement effects:
First with a Gradient Material set to transition from RGB 128 to RGB 129 and Displacement set to 100000%
Second is that gradient rendered to a TGA and used as a Displacement map
Third is that gradient rendered to an OpenEXR and used as a Displacement map
The Material is able to calculate an exact value for every