I wondered about age as I found it curious a puppy old enough to go to its new home had not been exposed to grass yet. Many breeders use what is called the Rules of Seven.
"By the time a puppy is 7 weeks old (end of seven weeks) it should have:
1) BEEN ON 7 different surfaces:
Carpet Concrete Wood Vinyl Grass Dirt Gravel Wood Chips Newspaper Etc.
2) PLAYED WITH 7 different types of objects:
Big Balls Small Balls Soft Fabric Toys Fuzzy Balls Squeaky Toys Metal Items Wooden Items Paper/Cardboard Items Milk/Soda Jugs Etc.
3) BEEN IN 7 different locations:
Front Yard Back Yard Basement Kitchen Car Garage Laundry Room Bathroom Crate Kennel Etc.
4) BEEN EXPOSED to 7 challenges:
Climbed a box Climbed off a box Go thru a tunnel Climbed up steps Climbed down steps Climbed over obstacles Played hide & seek Go in & out doorway with a step Etc.
5) EATEN FROM 7 different containers:
Metal Plastic Cardboard Paper China Pie Plate Frying pan Etc.
6) EATEN IN 7 different locations:
Crate Yard Kitchen Basement Laundry room Bathroom X-pen Etc.
7) MET AND PLAYED WITH 7 new people: including children & the elderly"
One reason they follow these is to have a puppy exposed to as many things as possible which make rides to the new home and other transitions go much smoother.
Flying a puppy is a personal decision and one of individual comfort. I have made the same length of a round trip you did to pick up a puppy before. Although this Cardigan baby was about a month older and had been socialized to a wide variety of things. He slept most of the way, potty breaks were not a problem and he was a content little traveler. I've made a three day round trip to pick up a puppy as well. In both cases, visiting with the breeders was more of an educational and mentoring time so there were ulterior motives
involved in the trips and I wasn't by myself on either of them. Again the second puppy was a bit older than Chip and a happy traveler.
There are a wide variety of ways breeders do things, so please don't take this as a slight to Chip's breeder. It isn't intended as that at all. On another list there was someone who did fly in their puppy at about Chip's age and it wouldn't eat from a bowl. When the owner's questions were finally answered, it was discovered that he had been free fed either out of a paper container (like a french fry tray) or on the floor of the kennel so the puppy had no frame of reference for a bowl.
However the more conscientious breeders do try to expose puppies to as many things as possible, often begin crate/housetraining, leash training, etc. All these things help to make a puppy more confident, take to transitions and adjustments more easily and give new owners a head start in enjoying their puppies.
Debbie