UPDATE: I have run some tests and yes, you guys are right. On several RAW files I tried variations of -100 on fine contrast and +100 on all three of the shadow contrast, mid-tone contrast, and highlight contrast and vice versa. I could see no difference between these files and the unedited RAWs. None whatsoever! I am surprised and a little disappointed.
All this time I thought that Contrast applied global contrast over the whole image, Microcontrast applied a very tiny(between pixels) contrast to the entire image, with the Advanced Contrast sliders varying normal contrast(same as Contrast slider) in their respective areas of influence(shadows, mid-tones and, highlights). Then the Fine Contrast slider provided an extra layer of contrast globally that was somewhere between microcontrast and contrast. This is not the case as the FC slider performs the same duties as the AC siders do, only globally instead of locally.
This arrangement puzzles me as I now see very little use for the FC slider at all. My usual workflow has sometimes included adjustments to the Selective Tone sliders and AC sliders in tandem in order to get the tones and contrast as I like it. Then when I finished with these I would decide whether or not some contrast, microcontrast, or fine contrast should be added or subtracted. I’ve gotten some beautiful edits this way, but imagine my surprise to learn that adjusting the FC slider was only messing up my precise adjustments to the shadow, mid-tone, and highlight sliders.
Using my workflow, I now see little use for the FC slider at all. The only two possible uses that I see are: 1.) if I want to increase or decrease FC globally it saves me from having to adjust all three AC sliders to the exact same point. 2.) If I want one or more of the AC sliders at more than +100 or less than -100, then I could adjust say highlight contrast to -100 and FC to -20, if the value that I needed was -120.
These two scenarios would rarely happen to me so I don’t see needing to use the FC slider but ever so rarely. I guess that will teach me not to read manuals.