Working Profile Tone Response Curve

If one selects a custom tone response curve, there are 2 sliders, one for gamma and one for slope. Wouldn’t setting the gamma usually set the slope to whatever one gets with that gamma? Would a gamma of 1·0 imply a slope of 1·0 or a slope of 0·0?

What is the standard slope for the ProPhoto colour space? I know the standard gamma is 1·80.

Finally, what effect do the two sliders have? RawPedia implies they have no effect as it states:
Note that the working profile will only specify the red, green and blue primaries, gamma will not change as RawTherapee's processing pipeline is floating point with no gamma encoding (that is gamma = 1.0). Some tools (like curves and histograms) will still display with a gamma (usually sRGB gamma) which is hard-coded for the tool and stays the same regardless of working profile.
However, changing the gamma does change what is displayed, so obviously there is an effect.