To lessen your confusion, if the omega and alpha meet and are a fated pair, then the omega will go into heat, even if it's not their heat yet. Most people call this false heat, because it wasn't in line to the omega's heat schedule. I don't really know how to explain it, but once you've already read alot of omegaverse manga with fated pairs then you would understand.
because it's a unique situation. the "heat" is a normal occurrence in omega but the "destined pair" is a special case between an alpha and omega. it's like all hell breaks loose if you meet your destined pair. the gravity/force between the destined alpha & omega is so great their senses go crazy when they are close to each other.
ofc, the normal way is to find an alpha and vice versa. similar to serendipity/soul mates in real world, "destined pair" thing is very rare in the omegaverse world. this is not a different concept, it is included in the omegaverse since the beginning. it is mentioned on that pamphlet-y first pages info. you might want to read it.
Well...i'm confused, in the other omegaverse, omega only unable to control their sexual desire when their on 'heat'. It's the same concept as ovulation in real world right? But in this story, omega seems horny all the time when he near his designated alpha, eventhough he's not in the 'heat time'.