Here is a visual demonstration of the effect of Clip out-of-gamut colors control. It demonstrates that a particular RawTherapee tool can work well with out of gamut colors.
The starting point - Neutral profile applied to a RAW file.
+3 EV Exposure compensation is applied. This multiplies the image with 2^3 = 8. Some of the colors inevitably become out of gamut with respect to the Working Color Space (ProPhoto).
Color Toning (method Color correction regions) is applied. This multiplies the image with 1/2^3 = 0.125. The result is an image without sky because the out of gamut colors are clipped.
The control Clip out-of-gamut colors is switched off. The result is the same as the starting point.
The used RAW file is taken from PlayRaw. It belongs to Alessandro Amato Del Monte.