My neighbor breeds Havenese dogs, and she does the same thing. The pups are fixed before the new owners pick them up. Just going by what she has done, i have never seen anything bad come out of it. She has never lost a pup during surgery..... So i think it is very common that breeders do this.
I think its fine to neuter pups that age. Maybe the only exception would be for x-large to giant breeds. If the pup is in good health and meets the min. weight requirements for the procedure than more power to her. Plus she can guarantee there will be no oopps litters from the dogs she sales if she alters them before she gives the pups to the new owners. I applaud this breeder.
PS most shelters also alter pups this young as well.
The vet clinic I work at does some at that age for breeders or the humane society. I've never seen to may problems with it except in large and giant breeds that need the hormones for all the growth they have to do. I do think it can be a very good and responsible thing to do to prevent puppy buyers from breeding if the dog shouldn't be bred.
I would love to have all my puppies altered before they leave for their new homes, if it could be done safely. Now my vet's been telling me that anesthesia is just too risky for puppies that young. He said he would never even attempt to put an 8 week old pup under anest. unless it was a life threatening situation. I have also heard that spaying too young can cause bladder control problems and neutering too young can cause some other problem (was it thyroid?). I am really interested in any input from anybody on any experience with this because as I said, if the day comes where early age spay/neuter is safe I would have all mine done before they leave.