Yes and no. I used to reapply Fluid Film during the winter, when it looked like it was getting thin. On that car, several years later, I went to install a trailer hitch. I zipped out a bolt and when I went to reinstall it (or maybe the kit had a new one), I could not put it in. The threads were too rusty. Rust inside of the unibody "frame rails". Despite it all looking ok, car was rusting in areas I could not see.
Later on, same car, one day I elected to pull back the wheel well liners. Sure enough, packed full of dirt. And some rust... which was perforated. Was pretty clean underneath but still, rust hole. Plus the the entire exhaust system looked kinda sketchy, 10 or 11 years of road salt meant zero bolts would ever turn again, and the pipes were looking a bit thin too.
Undercoating slows down the inevitable.