It seems to be nothing more than a conveniently not-wordy designation for 'drow that don't follow Lolth' in the game. That being said, it is inconsistent. Minthara isn't one, even though she doesn't follow the spider queen.
There's also the issue that for some bizarre reason Larian decided that drow eye color changes when they renounce Lolth, and the reverse as well. Doesn't exist anywhere else in any preceding novels or sourcebooks-completely unprecedented, and tbh....kinda uncomfortable IMO. Again, pretty inconsistent. There are actuall very few drow in-game you can meet that follow Lolth, but some are arbitrarily 'Lolthsworn' with the red eyes, while others are 'Seldarine' With blue/purple eyes (supposed to be rare eye colors in previous material, but near everywhere in BG III)
