Yep, this is the way the Tennessee Walking Horses are posed for stallion poses to get good photos for advertising and yes, owners and trainers are responsible for teaching them to park out...just takes 5-10 minutes. We also do this for pictures of yearlings we have for sale. The owners or trainers are also responsible for grooming them for photos.
I've seen PJ work. She is so good that when she arrives to do the shots, she only has to take a few. The horses stand perfectly still.
I used to have a trick for taking pictures of our yearlings. To get their heads up and ears up (BOTH at the same time) I'd shoot a water gun at them, aimed at their nose and say "ears" at the same time. Heads and ears come up pronto. After several times, you can put the water gun down and just point and say "ears" and it works beautifully. I expect someone to say shooting water at them is cruel, but I've never been injured by a water gun. My little brother had one and I survived. All I had to do was say "come out" to get them to park.
Here are the two picture the horse show photographer made of my filly that I raised and trained. She won the Yearling Filly World Championship and went back in that night to win the Yearling World Grand Championship. I thought I was a smarty pants that night because she beat my hubby's filly. His got 7th in the Filly Championship and 5th in the Grand Championship. They were the only two fillies in the Championship. All the other entries were colts.

I noticed that all of the horses are posed on ground that is not level so their hind legs are lower than their forelegs. Since all of them are like this, is the objective to create a sloping topline? My husband and I used to breed, train and show German Shepherd Dogs where a sloping topline is desirable. So much so, in fact, that we have even seen handlers carve out a shallow depression in the ground with their heels so the dogs' hind end is a bit lower to give the impression of a sloping topline. Just curious.