I'll answer the question asked of me one more time - "sigh".
All E6 films require some form of formalin in the process for proper dye stability. If it is not used, dyes can fade and a yellow stain can form. In Kodak and Fuji E6 kits, this is supplied in either a pre-bleach bath or in the final rinse (stabilzer) in some cases.
It was shown that adding the chemical reversing bath to the color developer was not a good idea. That is why Kodak and Fuji keep them as separate stages, as it increases capacity and lifetime of the two solutions.