But I can’t vouch for the accuracy of the book, but I suspect it was an approximation.
The haemoglobin and melanin are roughly in separate layers of the skin. There is an approximation known as Beer-Lambert that models the skin as two semi-transparent layers. This ignores subsurface scattering, but is roughly correct.
So, in theory two acetate sheets might replicate this. That’s my intuitive opinion. It has been many years since I did this work.