Yes, it does, it helps a lot. It’s essentially what I thought it must be doing, except that the application of it was giving me results that made me question if I was right. For example, on a test image, I picked the sky and all of it, plus any other similar shades of blue, were initially selected. I then reduced the bottom slider of the lightness slider to reduce its importance, expecting the mask range to increase and include darker and lighter blues (because Hue is set to max importance). However, I noticed on my test image that skin tones were selected after reducing the L weight to 0. This was surprising as pinkish skin is a very different hue to blue sky.
Perhaps the sky in this image didn’t have a strong enough hue to limit itself to just blues, and when I reduced the L slider, it started to incorporate more neutral tones.
Anyway, thanks very much for your help, that clears things up a lot. I just need to practice more…