Not only to prevent fungus on the film but mainly to prevent that the not used color stabilizers are going into a de-stabilizers.I hope you are not washing again after the stabiliser? You need the stabiliser to dry on the film. It is there to prevent mould/fungus growing on the film over time.
Pre-soak you can do to have a quicker warm up to 37,8C of the film drum. The C41 dev. temperature is pretty critical in the right temperature and time (3:15 minutes).