
It's because they're not from pure breed omega and alpha. If I understand it correctly, normally half breed would have diminished alpha omega function. President Seo shouldn't be able to produce an offspring, similar to how Youngjin should be unable to bear any offspring too. Not only that other functions also reduced - President Seo unable to sense any pheromones, Youngjin not going into heat, etc. For some reason, due to mutation, they don't have this inabilities and their functions work well. The thing is, it only work between both of them. So it also implies they're each others fated pair.
When the baby is born, it will be in a mutant form because both Youngjin and President Seo are not normal to begin with. The baby is like the perfect version of breed.
wait im curious. i forgot because the translation at that time was wonky but why exactly were the both of them unique in their species? from what i can remember they were unique from other omegas and alphas but idk why