I never thought about that concept until a day when I was making an effort to bring a dog down a bit before an odor imprinting exercise. I was just tired of her pulling my arm off and wanted her to calm down and listen. I also thought she would do better at the exercise, and she probably would have but my boss at the time told me to let her be high...
Later I asked why and what he said made a lot of sense. "She has to learn to think when she is that excited."
Based on his instruction and the statement I believe he meant "If we never train the dog when they are hyper excited, they won't be able to perform when they are."
"Happy bumpers" can be valuable to build or maintain drive either right before or in the middle of a drill using static objects. T work is perhaps the place they seem to make the most sense.
No different than giving a dog a few treats simply for paying attention prior to starting a more complex exercise.