I wouldn’t say her design was meant to look gayish. People do code their outfits and hair to appear one way or another, and when it comes to Overwatch this is doubled down on- character designs are meant to reflect gameplay mechanics, backstory, etc. But I’d argue that the short hair wasn’t really any attempt to illustrate her sexuality. Instead, it’s more likely that having shorter hair is more conducive to her high speed potential, as the wider surface area of more cisnormative (the long hair women are generally told to have) hair could create more drag and slow her down. This can be seen in the Slipstream Origins skin, which depicts her in her fighter pilot outfit before gaining her time-controlling abilities, and in all skins afterwards chronologically. Her skin-tight suit, jacket, and Pulse-Pistol holsters (her little arm gauntlet thingies) are also built to maximise her aerodynamic potential, at least in theory.
It’s also easier to animate- long hair would require a more sophisticated physics engine to accommodate that long of a hairstyle moving so quickly. With D.va, her slow movement speed outside the mech allows her to retain her long hair and still make it look realistic and reliably non-buggy. Tracer moves at much higher speeds per second and in much less predictable ways, which would probably cause her hair to flip in crazy and unnatural patterns and overall reduce the aesthetic of her as a character.
The likelihood of her short hair being a device to convey her sexuality doesn’t really seem like it has any precedence either. Soldier: 76, for however lazily it was introduced, is confirmed to be gay, something that took people completely by surprise, given that Soldier doesn’t really have any visual signals or any backstory to communicate that to the audience. I’d say the reason why that reveal was widely panned was because Bastet is a vastly inferior story compared to Reunion and spent little time actually developing its characters, but I digress. It just seems like the Overwatch team doesn’t generally employ visual storytelling when it comes to communicating sexuality, something I greatly appreciate- while I greatly appreciate openly and visibly queer characters, characters who communicate it more subtly can also be great characters when written properly.
Ultimately, if you feel alienated by Tracer being “gay” (she is gay, I don’t know why that’s in quotes), I can’t really say anything other than it wasn’t intentional. Zarya, a character everyone has presumed is queer, has not been confirmed at all- she’s a pink-haired omnic-distrusting weight-lifting hunk all on her own. The characters intended to be relatable aren’t meant to do so purely on the basis of appearance- Lucio wasn’t popular with players of color because he looks like them, on the contrary he received a boost in popularity when he began speaking the language and got more lore based around Vishkar’s abuse of his home, meant to parallel real life instances of colonialism. In my own experience I visually have many similarities to Mercy, (white, blonde, thin, blue eyes, I even have some German ancestry in me as well) but as a trans woman I probably relate more to Ashe or Sombra, having absent parents and being forced to find a way to scrounge it out on my own and be who I am in spite of what I was. It’s story AND appearance, with emphasis on the former, that makes a character relatable.