Garlean Third Eye Customization option

[kaynide]

Is there? It's kinda hard to look for since he doesn't even have a name, but the short story where it seems like this piece of lore originated from makes no mention of the sort.

Directed less at you specifically than the whole "is he isn't he debate"; as your link points out:

The boy Kan-E-Senna cured is referred to as a Hyur from Garlemald and not of the Garlean race. It's important to differentiate that there are Garleans (the race) and Garleans (the nationality).

Story from official site (Ameela's link)

Excerpt (bold for emphasis):

Clad in armor of the same unholy steel as the magitek monster which had entombed him, the Hyuran youth met Kan-E-Senna’s gaze. Not yet a man grown, there he lay, bloodied and battered on this godsforsaken battlefield.

...

Kan-E turned about with a start. Before her stood a young Hyuran in leather armor of the purest white—one of the Keepers of the Entwined Serpent, the Elder Seedseer’s personal honor guard, established in the wake of the Calamity.