Barracuda rear shackle question

It uses three bushes - two same as the lower and a tube tube bushing in the middle

I see that, but I think what is being missed is that the bushings for the bracket (tube section) on the body are still in the factory position.
A longer top bolt with a spacer/bushing isn't going to add any advantage at all.
If the tube that the top bolt goes through was as long as the bracket is wide, then yes I can see that spreading the load out over the longer area.

Oh, I see.
I saved the picture and then zoomed in on and see that the tube is actually extended out.

In the words of Rosanne Rosanna Danna, NEVERMIND :D