Which makes it sound like the dog had never set foot in a house
Or not that often, anyway. Yes, there is time for issues to emerge, but if the dog is settling well, that implies that it's temperamentally sound enough to handle change. Which implies good breeding or decent socialisation or both.
And yes, some breeders (and other owners) with 3-5 dogs use kennels, some of the time. You have workmen in and want 5 large dogs secured, and not to have to worry about them getting past a gate left open or tripping someone up. You have a bitch in heat who needs a break from the other dogs. You have a dog with an injury who needs a space to rest. You have a litter of puppies and the kennel gives them a bit more freedom than the whelping box in the kitchen, as well as fresh air without the worry of them finding stones and slugs to eat, so they go out there for a few hours a day.
I know quite a few dogs who move between house and kennels, depending - gundogs and farm dogs.
And yes, kennels can mean puppy farm, but they don't have to. In this case, puppy farm seems unlikely. The breeder chose to have the puppy operated on (££) and to keep and feed the puppy for an extra 3 months (££), so I doubt there was much if any profit left after that.
I'm not saying this breeder is a saint, but they are unlikely to be the devil.
OP, I hope everything continues to go well and you and pup have many happy years together.