Conventional dog training demands holding the dog on the shot rather than letting it break after the bird. Even in New Zealand, where hunting is not too formal there are pedants who are scathing about dogs that break. These are mainly duck hunters, where there is a clear reason for holding the dog.
I take the exact opposite view to conventional wisdom. I hunt upland far more than ducks, and the demands of upland shooting are different to waterfowl shooting.
I want my dogs to break on the shot. By doing so my dogs retrieve a few extra birds a year by following them by eye when they fly off crippled.
The hunting conditions where I hunt mean that a bird that flies off crippled has a lot of thick cover to get into, and it is hard to mark because of the cover. If my dog can see where it is going I want him to chase it straight away and retrieve it.
Every season I end up retrieving one or two birds that I doubt I would have. I hit them hard enough to cripple them but not hard enough to kill them. They fly for a while then hit the ground. I want my dogs to get onto them as quick as possible, and so I let them break.
Unlike with waterfowling having my dog break does not scare away any birds. So there is little point in holding him back if it is going to cost me retrieved birds.