SchH is a breed test and sport, and the standardization required for that means that the protection portion is rather ritualized. Not all dogs who do well at SchH protection will do well at "real" protection, though some certainly will. Conversely, not all personal protection dogs have the nerve and balance of temperament to be able to do SchH.
SchH work can identify if a dog has the traits needed to do real protection work, and can provide a very good foundation for later work in that area. However to make a dog a true PPD, additional training would be required. How much additional training would depend on the temperament of the dog and how the foundation and SchH training was done.
Whether a dog will truly protect in real life is more to do with the dog's natural temperament and character than anything else. Some untrained dogs will, some trained dogs will not. While a GSD *should* be naturally protective, not all are. Training in this area will not only answer the question of if the dog will or will not, but also will give the dog the skills to do a better job of it and ensure that the handler has control.
Both SchH and PPD require a huge commitment of time, effort and $$ and cannot be taken lightly. A true PPD is something very few people really need, and even fewer are prepared to commit to it in terms of ensuring GOOD training (there are a lot of bad trainers out there peddling unstable, dangerous "protection dogs") and maintaining that training, training themselves and their family members in the responsible ownership and handling of such a dog, and then making the lifestyle changes required when owning this type of dog.
I mean anyone can have a personal protection dog (federal permits allow the dog to go ANYWHERE) but most of the time you have to have a real need for one.
Absolutely NOT true. There is no federal permit for PPDs and they cannot go anywhere. There isn't even any standardized training or certification process for what constitutes a PPD. I think maybe you are confusing them with service dogs for disabled people?