I can see why that’s confusing haha. No, non-breeding just means that the plumage is not the “mating” plumage for the bird. Birds molt roughly twice a year on average, and sometimes due to being a juvenile or other factors, they just don’t molt into their bright plumage for attracting mates. Usually this looks similar to the plumage of the bird during the winter, or like female plumage of the same species.