I understand this "Half-omega" as incomplete on Doyun's part. Not Half something else.
Like in a study I read talking about women in Sicily that are only half-women because they can't give birth. And only those who gave birth are considered complete women. I find it fits Doyun's description quite well.
He can't give birth until his pheromones came and because he fell for a man, his body is developping to be able to create life and become a complete person, a complete omega.
Ha, I love this story too much (▰˘◡˘▰)
Oh, that does make sense! It was weird how they keep emphasizing "half omega, half omega" in the story and I just couldn't comprehend how he could be half something and half "nothing", genetically speaking. It's like saying you're half American but then leaves the other half of your genetic make up/identity as blank or 'nothing'. It's weird. Your term "incomplete" is a more fitting description/analogy, indeed.
It confused me a lot because, I understood how they have 2 genders/identities: human, male/female, and then their 2nd gender, alpha, beta, and omega. They could be a (human) man or woman and an alpha/beta/omega at the same time. But it's so bizarre when you're a man and a "just half" omega -- half omega but half nothing! A part of your identity is missing or incomplete! That can't be right?
Can genetics be like that? Is it possible for you to be this incomplete? But if it is (since this is fiction and it's not like the whole storyline and background of lore has been revealed yet), I can understand now why Doyun's so subconsciously insecure and distressed about his omega identity. Why everyone around him wanted him to develop normally as an omega rather than stay dormant and un-omega like.
That makes sense too! He could be a full omega, just labeled as half because of his dormant omega qualities.
But why were they dormant in the first place? Why did he grow with an alpha physique and strength? Is that how it is when people's second gender lay dormant during their body's development or for the majority of their lives? Or is it because he has 2 second genders fighting for dominance? A dominant alpha gene and a recessive omega gene?
Honestly, Doyun's case intrigues me more than their romance sometimes hahaha

He might be half-alpha, half-omega.
Omg he might be half alpha half omega. Body, strength and temper of an alpha, sensitivity of an omega. Doyun might actually have a sunny personality, too, that he just hides, based on the happy faces and fluffy aura he emits sometimes recently, and the usual couple photo at the end credits. How interesting~ Doyun sounds real cute~ now if only he wasn't so tsundere sometimes...