Save Displacement Maps as XX_displ.tif using DisplacementMap in CryTiff. The engine will auto use them as Displacement Maps for POM / Tessellation.
It was changed to this to save on performance rather than using the alpha channel. Now the engine will just use the _displ.tif file if it exists, so we're down to 3 channels (RGB) instead of 4 (+alpha)
Putting the heightmap in the alpha channel isn't the way to do it now. It's performance costly (ish).
Displacements Maps should be labeled XX_displ.tif
Normal Maps should be labeled XX_ddn.tif
Specular Maps should be labeled XX_spec.tif
and so on ...