I get not wanting to be intrusive to anyone, but couldn’t you have also solved this by just allowing the player to name them themselves? Then the player can interpret it however they want anyway
Since it seems like people are going to keep asking, here's why it is the way it is.
Doing those are the definition of intrusive. They force a player to sit there and manually name relationships between both parties for every character before you can even start the game. Especially in a game like this where you can't type, for anyone who doesn't specifically like incest, it's a waste of time and can be extremely annoying. Having that be the first thing a player sees is simply bad game design and can lead someone to just delete the game and not ever actually give it a try. Since it doesn't have any real function outside of it being a way to get around incest rules. Some games even just ignore what you wrote and explicitly name them with their intended relationships anyway. Just having these inputs make it pretty explicitly incest too. I've never played a game where you input relationships and had it be able to be interpreted in any other way.
For me personally, every time I boot up a game and am met with one of those screens I immediately turn it off and delete the game. Not only is it annoying, what you input is regularly ignored, and every game that has it is very obviously incest, but I don't even know if I like the game yet. I did not want that for this game. In this game especially doing it would only annoy at least about 1/3rd of the player base. Since it can't be incest for anyone who plays the black version. Since you're black and they're white. And that's roughly how many people play that version based on the tracked downloads.
Imagine if when you booted up the game you not only had to input the relationship between you and Ayako when the game starts, but you had to input your relationship for every single character. There's more than 20 characters currently in the game, around 50 if you count all the random characters separately. Would you want to input relationships up to 100 times (2 for each character, one for what they are to you, one for what you are to them), just because someone else may want someone like Madison or Sakura to be labeled as their friend's mom? I wouldn't think so, and forcing you to do that so someone else can have something explicitly stated in-game isn't really fair to you. It would feel like a huge waste of time and be super annoying. That's what it's like making someone who doesn't want incest have to go through the trouble of labeling character relationships.
On top of all of that, one of the biggest guiding factors of WW is not having to wait to get to the good stuff. Since nothing is more annoying than being excited to sit down and play an adult game and then having to sit through an hour (or more) of setup and exposition before you get to actually see anything. Even more annoying when there's always huge gaps between scenes. So WW isn't a super story heavy game and is designed so that you should always have access to a scene within a few minutes. The only exception is the lab story, but I did my best to keep that as short as possible too, and even put a scene in the middle of it. Some people like more story driven games and like that waiting, and there's absolutely nothing wrong with that, but that's not what I want out of adult games and so I made my game with a focus on gameplay and access to scenes. Since there isn't a story focus, having people go through all of the trouble to name relationships for these two specific characters from the start of the game is kind of pointless. They aren't ever really referred to as anything but their name beyond the intro, and you don't even ever have to interact with them if you don't want to. Forcing players to take time when they first boot the game to label characters they may not like or ever even unlock is a waste of their time.
That's why I did it the way I did. It's a compromise for people who want incest to be able to interpret it that way, and for people who don't like it to not feel forced into it or feel like they're wasting their time or be immediately put off the game. People can interpret the initial labels however they want without disrupting the game for anyone.
Hopefully that makes sense!