That is somewhat true. However, If one knows the basic developing material
used to develop the image, you can easily determine the basic type of
sensitizers used. If you know the dyes or pigments, you can easily
determine other things about the process. Trial and error and a little
experience will allow someone who understands a bit about chemistry -
especially photochemistry, to work backwards and get a good idea of the
Seemingly complex chemical processes are reverse engineered in this way.
All you need is some basic ideas and your set to go.