Other than that, all the dynamics are the same. I'd posit that in a world where no sexual preference bore any stigma, conversations between gay and straight partners would be exactly the same, save for the pronouns.
It's not that simple, I'm afraid... the dynamics are different, and some of the roots of those differences do exist at an intrinsic level, no matter how much we try to adopt an unilateral outlook and behaviour.
That aside, yes, orientation and preference does have a point, because these things aren't simple binary switches; people are unique and individual, and the degrees to which they are open or willing to experience various things are a spectrum. The purpose of making characters playersexual, rather than just universally bisexual is so that different preferences and sexualities can be displayed, without actually hard restricting the player's hopes, and making it so that, by convenient coincidence, they are actually able to pursue the character they are taken with, with theirs.
More to the point - a world where everyone is open to sexual intimacy with everyone, regardless of anything else about them, as an enforced universal truth, simply feels fake, because that's just not what people are like... and no, personally, I wouldn't want to live in a world where everyone was expected to be okay at a personal level with everything, because it would take something away from people, rather than giving it to them. Also, you'd have to start drawing lines in the sand anyway, because sexuality, sexual preference and what people like or are okay with goes well beyond 'boys and/or girls'.
Like it or not (and not liking it is fine!), but within the context of our media, characters being coded to be identified in certain ways is a thing - it's a way of signalling without being overt about it that all human societies all over the world have developed in different ways, quite independently of one another, because it is quite natural at a creature level for us to do this... and it has permeated forward through all of our higher-order and advanced civilisation trappings.
Taking it back to a basic level, for example, I am a very bisexual woman, and then some... but the dynamic I have with my male partners is different from the dynamic I have with my female partners, which is different again from the dynamic I have in multiple partner situations... they are intrinsically different experiences, and in any relationship where sexuality is a part of it, the intrinsically different experience and nature of that aspect causes intrinsic differences in the rest of the relationship naturally - and that's okay. It's a good thing. But it means that out there ,there are people who would not at all be interested in me - and that's okay too. In between that, there are people who might never consider themselves open to a certain type of intimacy, until a particular individual turns their head that way; they may not have physical attraction to that type of person normally at all, but this particular individual is someone that, because of everything else about them, they can see themselves with, and it tips that balance into a willingness to try with them what they would not with someone else. I've seen this before in fact.
So... when a character exists with an entirely heterosexual background, as far as is visible in the depiction and information available in game (Wyll - he might be anything, but in terms of just what we see directly in game, and the absolute information we have, and his general media coding beyond that... he's purely heterosexually-facing), when they are in fact open to romance from a same-sex character, it feels contrived and fake if there isn't some kind of lamp-shading to acknowledge that this is different from what we know and have seen so far; having a conversation about it not only adds depth and uniqueness of the character, but it gives the player chance to define more of their character tote game, which the game can potentially take on board and work with later.
