I have known too many masters who thought they were above the leash law.
The dog is described by the family as a “typical, playful, one year old.” I love my dog but I’m willing to bet that the dog wasn’t acting “playful” when he went after the mail carrier. The parents failed to restrain their dog and the fact is, too many mailmen are bitten - sometimes seriously, by dogs. The homeowners are at fault - period.
The mail carrier had no choice but to try and defend himself from the DOG. If you are going to own a dog, make sure it does not bolt out the door!
When we had puppies, opening the door was done systematically and carefully. My sons had no doubt that it was a huge deal to keep the dog in the fence or in the house. But it was a major effort on our part of total control until everyone knew how to do it and was mindful of it EVERY time a gate or door was opened. You don’t even open the door until you have figured out where the dog is and that it is under control before you open it!
This is why many people are not able to own dogs without tragedy. They don’t control themsleves and their kids - forget the puppy.