Confused about Parallax Diffuse Shader

from the documentation it says:

“The Height Map is contained in the alpha channel of the Normal map.”

If that is the case, why does it have two boxes, one for the normal map, and one for the height map?

This leads me on to ask if I can check that I have the following correct:

definitions:

Normal map: is used to add surface detail to make something appear more complex, the detail could be height; messy looking map means more detail.
Specular map: alpha channel of the actual texture, black is dull, white is shiny; clean looking map with just gradients between b&w

Shaders:
Parallax Diffuse: uses normal maps for detail; confused about how the height is taken, hence above post
Parallax Diffuse: uses normal maps for detail; alpha of main texture for shiny, same confusion for height.

It turns your textures into sludge. Thats what it does.

…honestly i never could figure it out…

okay, I don’t disagree with that.
The problem is that I was planning on using one for normal buildings and the other for glass ones.

Do you have a better suggestion then please?