Okay, this skill is supposed to do two things, but I'm confused about it.

When it says that light armor "weighs nothing", does that mean that this happens only when you've equipped it, or does it always weigh nothing when in your inventory?

When it says that it "doesn't slow you down", what does this mean exactly? I have seen absolutely NO difference in movement speed or stamina when wearing light armor over regular clothing (no armor at all). I have timed myself running with just clothes on vs light armor and have not seen any difference whatsoever. Perhaps it only refers to sprinting or lateral movements?

Also is armor weight cumulative? If I ONLY have light boots on, would I take as much movement hit as I would if I were wearing guantlets, a briastplate and a light shield?