Did you use a bump map to at more detail to your normal map?
Also, a leafy ground would have a subsurface, or just more contrast variation.
It’s just a matter of making your material look like a photo (as if that makes it easy). It can take a lot of tweaking in many different areas to achieve photo realism. (For the curled up leaves, your could create a mesh that looks like a curled leaf and place it where you need to)
TBH though, those screenshots on the “real displacement” article don’t look like they were just created in SD and dropped into UE4. They look like there is some heavy editing under the hood, in the material editor. Sadly, I don’t fully understand the material editor yet to help you much with that.
That material is already nice looking, Achieving complete photo realism, unless your doing Architectural Visualization, is unnecessary in my opinion.
I know this wasn’t super helpful, but I try.
Hope this helps!