Being an alpha, I think that the doctor wouldn't be so calm in a room filled with omega pheromones, even thought there are alpha pheromones around too. Instead he is not affected by the atmosphere, so or he has already mated or there's another bond between the two. And yeah, I remember he is a familiar of Doyun.
Most if the omegaverses I read ler it clear a mated status only inhibit the omega part, the alpha still goes crazy, unless it's the "fated mate" I think, so I vote by the family status (even though some Omegaverses teach us that family blood sometimes can't stop the mate urge caused by the omega's pheromones)... Maybe the way the autor choose work the omegaverse is slightly different? lol
I'm afraid that the doctor likes doyun