Regarding this race database file:
https://i.imgur.com/lhItso3.jpg
I need to point out that some non-playable races have entries in the datafiles since at least WoD introduced mercenary mode. In that patch, they made transformation items also change your race. Before it, if you were an orc using "Orb of the Sin'dorei", you'd be listed as "orc" in your tooltip. Since that patch, the orc would appear as a "blood elf" in the tooltip (try it yourself in the game, transform and mouse over your portrait, check the tooltip that appears).
Since then, if you use an item to transform into a Naga, Vrykul, Taunka, Broken and some other non-playable races, your tooltip changes to show you as "naga", "vrykul" and so on. THis does not work on all NPC races. For instance, it does not work on ogre transformations.
I guess that is the info that we are seeing in that database image. Notice how Naga, Broken, Taunka and Vrykul are all there. Interesting that it also includes Forest Trolls, Tuskarr and Ice Trolls, but I don't know any powers that allow you to turn into them (well, there's the Elixir in Northrend!Dalaran sewers that has a chance of turning you into a tuskarr. I'll check it out when I get time).
The interesting part is that Gilnean human, Nightborne, Void Elf, Highmountain Tauren and Lighforged are different in the sense that they share some ID numbers with other races, while the NPC races cited above all are listed as "0". I think Gilnean Human may just be Worgen human form, not a real race, but the other 4 could be indication of planned sub-races.
Yet another evidence that nightborne may be blood elf sub-race! But I'm worried about "Void Elves". Be careful there, Blizz...
Anyway, this is not a file from expansion, and things will most likely change in 8.0. As far as we know, these entries may have no importance.