In defense of him, it said that male omegas are rare, 1 in 100,000 rare. More rare than albinos, 1 in 17,000. So to relate remotely to what he experienced, imagine you see an albino but you can't know they are an albino because they are wearing a wig and makeup. They are hiding it. In that case you wouldn't suspect at all they are an albino unless they tell you that themselves.
haha, I know. Also I think it's implied heavily why chayoung never noticed even though he even questioned gyuha for getting wet easily. when your childhood friend's parents told you that their son is a beta, questioning them is the last thing you want to do since you trust them like your own
chayoung, you had so many signs and you missed it. Cumming into your partner, losing appetite when gyuha's been vomiting and weak, excessive marking, wanting to always please your omega, etc lmaoo