Why?
Why can't she just have a relationship that is also gay?
Why does there need to be "more"?
I don't think you're understanding me right. The relationship can be "just a relationship that is gay". But the point can't be that the relationship is gay. There's a distinction there that makes sense in my head, but maybe I'm failing at explaining.
First and before all, it's as if you're making a distinction between a relationship and a gay relationship, which isn't how it works in real life. Or at least, how it SHOULDN'T work.
Secondly, I'll explain with an example. That example actually being the story DLC for The Last of Us. The main point of the story wasn't "Ellie is gay". It was about the player getting to know Ellie's friend, and going on the journey that lead to Ellie losing her. Her being romantically interested in Riley was there to amplify that main thread of the story, not just for the sake of it. And it just so happens to be one of best moments for gay characters that I've seen in gaming, easily, and even one of the better in pop culture.
So, I mean, can the plot point of "Ellie is gay" be the main crux of the story, or a major part of the narrative? Yeah, it can, but to state it simplistically, they need to make it work within the logic of the world and narrative. They need to tackle it from the starting point of Ellie as a character.
Nobody questions the relationship between two straight characters being important to a story, even in a video game. Even simple relationships. When Peach gives Mario a peck on the cheek, people don't say "ugh, sexuality has no place in video games unless there's a Very Good Reason For It."
The moment representation for anyone who isn't straight is mentioned, we immediately see it questioned. If Peach gave another female character a peck on the check as an affectionate reward, past experience suggests people would asking why a character's sex life matters, games are for fun, it wasn't like this in my day.
No relationships, outside casual hook-ups, are just about sexual orientation. Sexual orientation is what leads to people having personal relationships. It should be assumed that a character's sexual orientation will of course be about more than just the bald fact that they're gay, straight, bi, etc. Even if the story is simple such as "Jack rescued his girlfriend Jill, and they went home." People can be expected to assume they're off to do all the stuff people do when they're in a relationship besides just standing around telling everyone "Hello, we're heterosexuals."
When the characters are heterosexual, this assumption is usually granted. We life in a heteronormative society, so people don't even think about it. They've been taught to proceed with such an assumption. It's normal.
I'm sure there are a lot of people out there who think like that, but I genuinely don't.
The reason for a relationship between Ellie and another person to be gay is because Ellie is gay. That's fine, that's enough of a reason. But the crux is that there has to be a reason for
the relationship! You understand? It can't just be "because gay". The reason for the relationship between Bill and Frank was to show the player something more about Bill and what kind of character he is, and as a contrast to the facade he seemingly puts up for Joel. The reason for the relationship between Riley and Ellie was to amplify Ellie's loss. Hell, the reason for the relationship between Tommy and Maria was to give Tommy a reason to not take up Joel's offer, and to amplify his eventual acceptance of his offer, which in turn served to amplify the significance of Joel asking if Ellie was OK in that shoot-out.
Point being (and I know how negatively this can be construed, but I'm going to say it anyway) you don't need to go out of your way to make a statement. Like Bill and Ellie showed us, you can be subtle about it, and make it ring even truer and louder (in my opinion).
Thankfully though, given the examples I've been summing up, I don't think I'll have that much to worry about. Unless they take a 180 degree turn, they really know how to handle this kind of stuff.