This is not my video but I used to watch my pups and their mom play like this.
An old trainer told me once to leave my pups with their mom as long as you can because she will teach them everything they need to know. Queenie, the mother of my pups, would take squeaky toys and run with them while the pups chased her. By the time they were 3 months old they would even chase birds across the field as they flew overhead.
I was glad to see this video because most greyhound pups are not raised this way but it is how I raised mine. Most are raised in runs that are between 100 to 1000 foot long and about 20 foot wide. While there is still plenty of room to run and play, I think raising them in a field gives them that much more endurance. That is why I had so many double A dogs.
One time I walked out into the field while my 10 month old pups were running. I immediately had to drop to the ground because the whole pack would have run over me if I hadn't. Actually they did run over me but they jumped me as I was laying on the ground instead of running into me at full speed going around 35 mph.