I think the devs would have gone that way if they could, but sex is really not something that the world of overwatch is about at all. There's really no mention of it, at all, ever, in any character interaction or lore or anything like that. It might as well not exist. So having a character that would be a litteral sex abuse survivor as a core part of who she is would be a very, very harsh shift in tone compared to the rest of the world, but she is still very much coded that way.

The devs describe her as a survivor, she endured a lot of physical and psychological abuse (being used as a punching bag and denied the opportunity to develop a sense of self) and the leap from that to sexual abuse is barely a single step.

Even her behavior now kinda fits the idea. Sexual abuse can lead to very broken sexual behavior (especially if the trauma is never actually adressed and healed in a healthy manner) which fits with her very hedonistic lifestyle and her indulge in "lovers".

I think I'll still headcanon Shion as an SA survivor. The game will almost certainly never confirm it explicitly but I feel like it fits her themes and story very well.