*very carefully places this here in the thread, from a discussion in a discord server. Wonders how long till it burns up in flames*
And so we quote -
well, my belief is this, based on the lore the npcs gave in the Ivalice raid

Viera children look like their mothers till the age of 12, once they hit maturity, their real gender is shown. From there, the men come to the village to collect the now known sons, and take them away. Given no one has ever seen a "Male" Viera, no one knows /what/ a Male Viera would even look like-- and maybe, just maybe, they want it that way. They don't want people to know who is the male of a race or the female-- so the best way to confuse individuals who never seen such a strange genetic alteration based on the x n' y chromosome change is to dub one one race and another-- another race.

So, in essence, he Hroth and Veira are one and the same, but given the lack of understanding of their culture and how they operate, due to so much secrecy from their society... well-- people think they are different races all together.