Yes the explanation I gave was somewhat simplified for practical purposes. But in the end it is always about modulation of blue and green light hitting the paper. That is what the filters are doing, whether you use a single filter, or combine hard and soft filters in some exposure proportion to "build" the filtration of a single intermediate filter. As I said though this equivalence of course only applies in the absence of local manipulations during hard and soft exposures.
The principles are the same for additive colour mixing with blue and green filters (Beseler Universal VC heads for example). It's just a different way of getting blue and green light to the paper.
Originally Posted by Rafal Lukawiecki