Again if you are going to argue what’s in the food code, then if they do not spell out that Mayo is mayonnaise, and furthermore that it can not be a subject of an adjective that suggests a revision of the concept...
This sounds like a matter of some technical adjustments at worst. If we can have I Can’t Believe It’s Not Butter margarine, why can’t we have a Justice to Mayonnaise egg free sandwich spread. Also there is now a provision (for health’s sake) for “fat free” and “low fat” mayonnaise dressings.
That’s why we have courts
However, I would think there is a precedent established long ago by Miracle Whip.