Some comments suggest it's because it's cooked at a higher temperature than boiling. That doesn't matter because the inside of the potato obviously never goes above boiling, since it continues to have lots of water inside after being cooked. The same exact effect should be achievable simply with deep-frying the potato at the same temperature.
Other comments suggest something somehow preserves the potato's flavor more than other methods. But that's not how cooking/flavor works. If the rosin (or boiling water or frying oil) were seeping into the inside of a potato then sure any or all of them could be leaching out flavor compounds, or reacting with existing compounds... but they're not.
All this is doing is heating the inside of the potato, where literally the only variables are the amount of heat being applied and the moisture escaping at the surface. If you were eating the skin then yes there's a massive difference between boiling vs. frying vs. roasting. But not on the inside (except for how much water vapor escapes which is a question of temperature and wrapping). And this article is literally about eating only the inside of the potato, since the rosin itself is apparently not fit for consumption.
Best I can guess, this is just a novelty thing about eating potatoes encased in newspaper that has wound up essentially glued to a hard potato shell? Seems like it's more about the experience, and nothing whatsoever to do with flavor or taste.