I'm not sure about the difference in your screenshots - it looks a bit like the lighting changed, or the color of the cloth.
Remember that when using IR, displacement does not get recalculated when you move your camera. So if you zoom up close to your object, change something in the material so that displacement gets re-calculated, and then move camera far away, you will only see the small area displaced (the area which was visible to the camera previously). To trigger displacement re-calculation, you can change something related to displacement in the material's settings (like displacement strength, or just plug displacement map out and in again), or you can restart IR.
For the layered mtl, displacement is only considered for the "base material".
