Difference in the alpha rendering of the AUX textures

Repro

1. Take a copy of "viewer#1008" object from http://maps.secondlife.com/secondlife/Danger!%20Danger!/74/81/39
2. Unpack the 2 boxes and 1 Universal and add them to your avatar.

Observed: The "viewer#1008 aux" box is more transparent.

Original report

I would like to apply BOM AUX textures on the lashes of my mesh heads but I noticed annoying differences in their rendering when they are alpha (which is the case for lashes).

Here is an example : https://gyazo.com/a46d41f4fbbbb8588a82c71d69892870

Above, the texture applied directly on the prim.

Below, the texture applied through the BAKED_AUX2 texture.

As you can see the rendering is different. The BAKED_AUX2 is "lighter".

Why is it so ?

For the moment I can not use the AUX textures for my lashes because of that difference...

https://secondlife.canny.io/admin/board/bug-reports/p/difference-in-the-alpha-rendering-of-the-aux-textures

Reproduce the difference using the linked viewer#1008 object, comparing the AUX texture on lashes with the same texture applied directly to the prim. Start by investigating the viewer's alpha rendering paths for AUX and ordinary textures. Done means the two rendering modes produce consistent alpha appearance.