Hello Cliclasp, the Gambiers are certainly remote and further away from say, the Tuamotus, where Tahitian pearls are also cultured. They are a more isolated archipelago of islands, a relatively long plane ride away (4.5 hours from Tahiti, with a stop), further South, by the Tropic of Capricorn.
Some say that the luster profiles of these Mangareva grown pearls is higher due to the cooler temperatures of the water the oysters live in, especially during the Southern Hemisphere winter. A recent study by IFREMER, the French oceanographic institute, concluded that the ocean temperatures dropped enough during their winter to cause a metabolic slowdown of the oyster. This affects nacre deposition rates, and could be why the luster seems sharper in these pearls from the Gambiers.
In terms of the color, many think that pearls from Mangareva have some of the more interesting color profiles found in Tahitian pearls today. But that is not to say that producers in the Tuamotus, for example, cannot produce pearls with stronger, brighter, interesting coloration.
I think it comes down more to the skill of the individual producers, the quality of their grafts, their mantle selection, those kinds of things, as there are some farmers who noticeably, year after year, produce more color, and others who, even though they have farms in a great location in the lagoon around Mangareva, produce less interesting colors.
The thickness of the nacre is more a reflection of the amount of time the pearl is left in the ocean to grow. One could certainly grow thin nacre pearls in the Gambiers, that could not be legally exported from French Polynesia ( less than 0.8mm in thickness), by leaving them in the water say, for only 6 months.
Icyjade, I think you are correct in concluding that perhaps some of these unique colors, like the deep peacocks above, are signature pearls from Managareva. I haven't been able to find another similar looking pearl from anywhere else, but that is not to say they do not exist.