I’m not able to approach this from a scientific point of view, but from experience I can state that it makes a big difference when this input colour profile is applied.
I’ve been playing with the ordering as a result of the afore mentioned Red Lily or Daylily thread due to more extreme results when highlights are clipped if using a D750 profile.
In darktable the input colour profile is applied, by default, after exposure. I would expect this to be done right after demosaic. Easy to check if this has a better result:
Default pipeline:
Input colour profile moved to just after demosaic:
Look at the white bark.
Another example: Default:
And early in the pipeline:
The red “mist” on the yellow in the first one is interesting…
I know that both images have issues (first: Highlights are clipped, second: out of gamut), but still.
These examples are very basic: Standard modules, exposure + filmic (v4, scene referred) are turned on. All settings are as-is when turned on and all are cropped and the colour profile used is the one supplied in the Red Lily or Daylily thread.
I’m not going to make bold statements based on a bunch of test edits I made in the last, roughly, 24 hours, but it is obvious(?) food-for-thought and I am very curious to find out what others have to say about this (hopefully based on some science 
)