It is north of 62° latitude. However the second linked article has an error. Kotzebue is at about 66° north (NOT 69° as the article suggests).

Keep in mind that that part of Alaska is for the most part a very flat coastal plain. He likely had a good view of the southern horizon. The orbits of the GlobalStar satellites that the iPhone uses are optimized for the mid and lower latitudes where most of the worlds people live. In more northerly regions those satellites will be low on the southern horizon. Any hills or mountains to the south will tend to block the signal from the satellite. The 62° latitude that Apple quotes is no doubt a somewhat arbitrary figure based on your probability of seeing a satellite above the visible skyline. If this fellow had been in a more hilly (let alone mountainous) region, it probably would not have worked as well.