I dont recall how its portrayed in the manga but in the novel it specifically says aeroc was always an omega the drugs didn't alter his sex its more accurate to say his pheromones were weak and he even said he was never able to knot (if this were another omegaverse hes be a recessive omega), they said that is someone like kloff had taken the drug nothing would have happened to him
well he had a mutation that caused him to transform from an alpha into an omega, and i supposed the medicine expedited that process. i just find it hard to believe the natural process would involve him undergoing excruciating pain and internal bleeding, so i doubt kloff was administering it correctly
i love this story, but i am a bit discomfited with the messaging that aeroc must have his body mutilated into an omega in order to be worthy of kloff's love. i do think a lot of it is a reflection of the traditional and conservative omegaverse society in the story, where aeroc's inheritance is threatened just by him being an omega, but it still leaves a bad taste in my mouth. like i wish he could have just been loved as he was, rather than being scorned for wanting to be in an alpha/alpha relationship :(
ultimately the upside is that aeroc is able to bear his own children because of this, but yeah idk very fucked up tbh