In Japan I had some hard boiled eggs that had been seasoned through the shell. How'd they do that?

This one really stumped me.
I spent so much time speaking to chef friends and food buffs, perusing food blogs and even startling a few Japanese tourists (who then took my picture). No one had ever seen or heard of such a thing.
A thousand Google searches only turned up high school science experiments and neo-eggstremists. I'm not going to lie, for the first time I just couldn't find the inquirer any kind of answer. So when I sat down to write a sheepish email, halfway through I stopped, one more more Google search and then I could admit defeat.
By some miracle I entered just the right words and there it was in the first entry, a very brief explanation of how to accomplish what it was that I had been searching for: How to season an egg through the shell. Of course I was so excited I closed the window . . . never to be found again. Still the info was ingrained.
The solution? A solution . . . of salt and water that is. Simply boil your eggs however you like them, cool them and drop them into a salt saturated brine. To make this brine dissolve 3 oz. (7tbsps) of salt per cup of water. (it helps dissolve if it's hot). Leave the eggs in there for 36 to 48 hours and there you have it.
A perfectly seasoned egg inside of a shell.

I can't really think of a reason to make a habit out of this, since you essentially have to use a half a cup of salt to season what would otherwise take a pinch. But the process is interesting, and you could theoretically rotate eggs through a brine over time. Which, if hard boiled eggs are your on-the-go snack, could be pretty useful.