The stabilizer is a required step, see B&W film doesn't need it, because silver is a natural bactericide, in colour films the silver is fixed out, and bacteria love gelatin, so it needs to be poisoned in some way so that the bacteria don't eat it. C41 films now use a different chemical for this, E6 uses formaldehyde for this.
IIRC, the formalin in E6 is not just a bactericide, and there would be plenty of less problematic chems out there to do this. The formalin is necessary for dye stability, which is obviously not needed in silver grain based B&W and which has been made unnecessary in modern C41 emulsions.
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