Good question so in my speculations, I think the secondary genders exists but kinda mellow for the male omegas because they don't really produce a lot of pheromones, research in the dark is being done to get the eastrus pheromones on individuals (all genders cuz why not, imagine making two alphas pregos wow, happy, great times) anyways, the uke is oooobviouuuuslyyyy an omega and apparently bounding that long with an alpha without properly mating or doing the mating bound to be precise made him yearn for his alpha in the days he went for business... As such his heat awakened and as a result the pheromones exploded... And tada, everything else is just omegaverse textbook scenario
Ah
What happened?