actually it is the other way around, you CAN put the cock birds in the breeding area so they pick and fuss over who's going to get the best nest box and there is where you would keep your cock birds, when they get settled on their little piece of realestate you don't want to have to start over with all that fuss every year, then you can introduce the hens and they should mate up at some point, only pairs in the breeding area work better, then if you want you can remove the hens to another section for a rest period and then repeat when you want to breed again. I do not race so I let my pairs stay together...but thats just me.
I try to keep my breeders separated until breeding season, so that the hens do not waste their eggs and both cocks and hens will be fully rested and in good health for breeding. Then I pair them up myself, using individual cages. If I had a breeding loft, I would prefer to pair them up in the nest boxes, letting them out once they've mated and claimed that box as theirs. But since all I have at the moment are invididual breeding cages, I let them have their clutches in those. At least then, I know for a fact those birds are the bio parents of the babies, and no squabs or eggs get hurt over fighting for nest boxes.
You can do it either way. Pair them yourself, or let them pick their own mates. Whether you pair them in cages, the boxes, let them breed in the cages, or the loft, it doesn't matter. Do what you think is best.