Anti-seize lube is not a rust preventative. Some have a silicone grease carrier, which displaces water from the surfaces, but that's more of a side-effect.
Side effect or not, it is effective. The Motorcraft High Temperature Anti-seize Lubricant (XL-2) states "...and guards against rust and corrosion caused by chemicals and weathering." The Permatex Nickel Anti-seize states something similar " Salt, corrosion and moisture resistant." I wouldn't paint the bottom of my truck with it expecting it to prevent rust but for the application I mentioned it's ideal. Did I mention it's effective? Silicone Brake Caliper Grease (Motorcraft XG-3-A) would also be effective and acceptable for the application I mentioned.