For void elves, I think it means you can roleplay as a void elf that kept his normal skin like Alleria, or as a high elf if you so wish. But I think the former is the more likely intention of the devs.
And just to clarify: I have no problem with people wanting to be a high elf in the Horde. My problem is people spunning headcanon as if it were lore. There's nowhere saying Auric led a group back to the Horde. What is known is that he is or at least was the high elf representative that watched over high elf pilgrims on Quel'danas, and, as far as we know, is still an Alliance character, as the Auric's Angels team indicates. It's the part of made up lore that I get riled up about.