Yes, exactly @dolores_74 . I confirmed all the same with my experiments.
I might prefer to reword my earlier remark to be a little more scientific/accurate. I'm trying to keep these things firmly in mind to render without getting stuck.
1. "Layer" controls visibility in render output. Lamps are always invisible in render output (but their influence can be seen).
2. "Exclude" controls influence (visibility+other things) in the render output.
Environment is somewhat similar to lamps, but somewhat different (as I understand it).
1. "Render : Film : Transparent" removes the environment visibility from all render layers, but leaves the illumination.
2. "RenderLayer : Use Environment" controls ALL influences - enables/disables both visibility AND illumination - for the render layer.
(I started looking into this while investigating the other thread where you posted. I have learned a lot.)