Some questions about Materials in the Arch Viz sample scene

Hi guys

I downloaded the ArchViz project in the Unreal samples and have been looking at the material behind the carpet. It seems to make use of layered polygons, vertex colours and multiple bump offsets connected into the opacity mask. However I am still a little confused by the logic behind the material. If you know the answer could you help me understand a few things?
Starting with the green channel of a bitmap file as an alpha the author creates 4 seperate bump offsets that add back into each other later on to create some form of cumulative effect. I believe this is to offset each polygon layer differently but I am a little confused how this can be acheived because the only distinguishing factor between them is the amount of redness in their vertex colours. In the Vertex Colour box though you can see that the code is only able to process the blue channel of the vertex colours (The base polygon layer of the carpet is an absolute blue with the others going from straight red to black)

In the examples 2+3 the author lerps between two values that are the same with the Green channel as an alpha. Isnt this pointless? I would assume the result from this combination would be the same output as a standard 1 vector parameter.

In image 4 the setting by the author is multiplying a vertex colour value by 0. Would this not reduce the output to 0 also? Making the following Lerp process another situation of lerping between the same value?

Screenshots again

Thanks for any help you can offer