Many GSD owners meet their "Waterloo" of sorts and DA is one that has certainly tested me over the shepherds I have owned....my current one is the best at minding her manners but yet still is probably the most "tense" when minding her manners while encountering other dogs while on leash....off leash...not a situation. The video shows a dog minding it's manners over an inanimate object..not another dog on leash in close proximity which may or may not be just as hyped up to get to the other leashed dog....so I might suggest it is not that easy. I can, at any time make my dog wait or relinquish the highest prized items at my choosing BUT...the biggest difference is...when asking a dog to hold position or be "civil" when they encounter other dogs they do not get a similar reward as a dog merely be instructed to wait for a fuzzy toy on the end of a fishing line....the dog always was rewarded with getting the fuzzy toy...unlike a dog on leash getting a similar reward....the other dog.
However, I believe there is merit to the process shown in the video....teaching a dog to obey under distraction even if the reward IS the distraction perhaps leads to the dog understanding "good behavior" amongst it's peers.
I believe the OP asking if exposure to other dogs might aid in the desired behavioral changes....I cannot see any other method which would test the dog's ability in this department....however...having a command over your dog in other areas....such as holding a sit/wait for a fuzzy toy until released...most certainly would help build this foundation which ultimately comes to fruition regarding on leash DA.
For many, including myself it has proven to be a challenge but I can attest to the fact....that if you diligently work at it....it will change.