I've got a question on a different topic. A lot of people in the on-line SOP world talk about "pair breeding". I've never kept just one cock with one hen but have always found that more cocks and fewer hens meant worn out hens... worn out meaning they have lots of feathers torn out of their backs. Does that not happen in a pen with just one cock and one hen?
Pair mating is usually a temporary arraignment. I like to single mate. I like to emphasize a hen. When I do, they are only together long enough for me to get what I need from her. I am also rotating that cock among different hens.
But yes, left together for long periods . . . that could be a problem for the single hen.
Perhaps not though. He may lose some of his enthusiasm unless he is seeing other females.
In a flock situation, he is perpetually being stimulated and will prefer some over others.