Selecting the race selects the tags.
It's not intended to be an advertisement that tells us they aren't Elves. They just need to make it easier to access the TAGS so they can streamline niche replies or quirks attached to each subtype.
Just two points on these tags (and one on exclusivity of Drow 1 and Drow 2 tags).
Firstly, I'm not really convinced that the technical aspect of how to get tags is part of the explanation. (I mean, it could be, but that would mean bad programming and bad reasons.)
In Patch 2, when creating a Cleric and selecting Tyr as deity, the PC would get the tags "Cleric", "Cleric of Tyr" and "Good Cleric". Leaving aside that this is
ridiculously redundant, this has two implications. The tag "Cleric of Tyr" shows that the game is perfectly capable of creating a tag that is not just a function of the Race or Class variables. The tag "Good Cleric" shows that the code is perfectly capable of running a function on the character sheet and combine various character attributes as well as preset information (the god-to-alignment matchings) to compute and assign tags.
So from a code point of view, there really would be no need to make Drows a separate race, just so that 2 Drow sub-races can be created (there isn't a sub-sub-race level), and this just so that a certain tag can be attributed to the PC.
Secondly, a good User Interface provides a comfortable and intuitive experience to the ... users. Its goal is not to allow devs to code using the fastest solutions.
Also, if the game really needed to communicate "ah ha, the alignment that you choose for a Drow will be pretty consequential in terms of dialogue options", this could be done very simply by writing in the Drow description what to expect. This space is pretty much made for this kind of information. Trying to convey this "ah ha, you're in for a different experience" through making different races and sub-races, that have no established lore and show no mechanical difference, would be a really bad UI idea ("would", because I'm far from convinced this is what Larian is trying to do).
Lastly, regardless of the purely UI aspects, if Larian is trying to go for "these are Very Evil Drows" and "these Drows are not like the other ones", it would be a lot more interesting to give both types of dialogue options to both Drows. So that we have
agency in how we roleplay our Drow, instead of just following the script.
I mean, imagine I play a Very Evil Drow, who worships Lolth and all. I walk in the Grove, I'm desperate for a healer. I'd certainly tell people "I saved your skin" and "I'm not your typical Drow, I'm not a danger to you", if those options are available to me. Of course, after finding out that there's no cure in the Grove, if my Drow joins with Minthara, well, I will have lied. I'm Very Evil after all. My Very Evil Drow might find it quite advantageous to have access to both dialogues options.
