I presume it's just the universe the author wants to use. In some stories the pheromones dont affect anyone but the alpha paired. But in some cases they still do, but its just more geared towards the faited alpha. I presume this one is the latter.
In this universe, Apparently paired omegas can still affect other alphas. But it seems like the omega is the one who bears the chains, as their body seems to reject any other alpha other than their mate.
Fated pairing seems to be canon too.
It gets confusing sometimes with omegaverse stories because each author tends to tweak it to their liking.
Is anyone else confused why his pheromones still affect other alphas. I thought that didn't happen after being paired???