You have completely misunderstood the way a concave diffuser should be used for macro photography. As I originally designed both types of concave diffuser, and coined the term "concave diffuser" with regard to macro photography, I think I am best qualified to describe it.
The outline of both these principles is described here with diagrams. Please note the the end of lens concave diffuser is described in the diagrams as a "cup diffuser" because the first one I made an use was made from a plastic cup.
First of all the light source is supposed to come from directly over above subject. Likewise the end of lens concave diffuser is meant to go right around the subject at a close distance to it. In other words, the top of diffuser and the sides of it are supposed to be the same distance from the subject. It is designed to work in the true macro range. None of your set-up conforms to this at all. What is more on your set up, the flash is much closer to the centre of the diffuser when it is bent into a concave shape, than a convex shape. This completely distorts the results as the area of the diffuser being illuminated by the flash is much greater on the convex shape, than on the concave shape. In addition you have not curved the concave diffuser so it wraps around the subject.
If you want to genuinely test a concave diffuser as I designed and described it with this type of set up, your diffuser would be bent into a true half cylinder, and it would go over the top of the subject, with the flash above and firing down to it. Unfortunately the very detailed articles/threads where I first described how and why these principles work, on Juza Nature are no longer on the internet, as that version of the website no longer exists. However, this method has now been used all over the world by many macro photographers such as Orionmystery (Kurt) who have proved beyond doubt that this method works. This is the major thing. It has been proved by many photographers to work, and give the lighting most free of specular reflections on shiny invertebrates.
A discussion of the effectiveness of this method of concave diffusion can be seen on this Photography on the Net thread.
The method of concave diffusion with macro photography is for reducing specular reflections on the curved shiny surfaces of invertebrates. It is design to work at macro distances, where the diffuser is only a few centimetres from the surface. This is especially important for understand how and why this works. Lighting in the macro region is different than at longer relative distances. As I say, if you set up the diffuser as I designed it to be used, and use a curved shiny surface, you will see how effective it is. Plenty of others have already carried out these tests. The light source should be above the subject, in front of it to a degree, and pointing down, but not directly over the subject.