There is supposed to be an agent in the Flexicolor stabilizer that "sets" the color of the negatives to make it more permanent. In the older days, formaldehyde did the job, but after that hit the unwanted chemicals list, there are only traces of it left in the solution. Not sure what component does the "stabilizing" now, but I've used it for many years, as well as the Fuji Hunt and Russell varieties, and the film is definitely stable.
The E6 stabilizer has a slightly different composition, again, supposedly to stabilize the color of the dried film.
A good film wiper (or lint-free paper towel) needs to be used to remove the foam and excess stabilizer so the film can dry smoothly.