Yes, it is an original vanilla texture which is left unused. The way it appears in this mod is that the head model makes reference to the unused texture in the MDL file, the only reason a texture would appear in the mod is either due to a fix or because the texture isn't part of the PC game.
Did you read the part in the readme where it says her texture was ported from the Nintendo Switch version of Kotor? It isn't included in either the PC or XBOX versions of Kotor, I suspect (baseless theory incoming) that maybe LucasArts has some sort of archive of Kotor, it's engine and assets which were used in the development of the Mobile, Xbox One and Switch ports of Kotor.
In the Nintendo Switch version, the Female Dirty Commoner Head Variant replaces the Blonde White Commoner head (Ice's vanilla head etc.) resulting in this:
The Nintendo Switch's textures were, from my observation, probably upscaled from the original XBOX textures meaning 256x256 textures went up to 1K in resolution. Aspyr might've mixed up the Blonde White Commoner head with this unused dirty head from their resources and added it to the game, this is all just a theory. All that matters is that this mod makes it avaliable for PC players.
Here is the original Switch texture, the dirt on her face might be more noticeable with this texture.
comm_w_f02.tpc
Nope, the 1st Sith Apprentice head is totally unused whilst the 2nd version is the one we see in the vanilla game.
If I didn't remove the scar then the area of the head where the scar would appear would appear visually bugged, try removing N_SithAppren01_H from your Override folder and you'll see what I mean in-game.
There weren't very many appearances of the Sith Apprentice NPC model so I was left with very few places to restore the 1st Sith Apprentice head variant.
I did notice the sides of the ears look bad but I didn't notice this little bit on the side of the head, I would have to check on the side of the vanilla PFHA02 head and see if this bug exists on that one. If it doesn't then I'll need to investigate the unused head texture and see if I need to change somethings though if the bug DOES appear on the actual player head then I might need to report this to the K1 Community Patch github.