The diversity of puppy development can lead to litigation or bad reputation if the vet does not adopt a certain procedure during the first vaccination.
I had a phone call from a lady owner today. She said that the puppy was a male but was listed as a female in the vaccination card by Vet 1.
In this case the pet shop said the puppy was female. He had no scrotum and a "long urethra". So Vet 1 trusted the pet shop operator who is in the business for many years.
Basically it is common sense to examine every puppy prior to vaccination so as to avoid such rare cases from happening. Never trust the pet shop operator to give you the correct info or the record the info after you sign a blank cheque (vaccination record).