Why dog pack walks makes for the world's happiest dogs !
The reason why I say the 'fight or flight' issue is the most unnatural thing for a dog, is that while it is the natural response of almost all species when first exposed to large numbers of their own kind - dogs have the added bonus of being a pack creature that craves being in multiple dog walking and playing situations - ONCE they are social.
Humans are also supposed to be social creatures, so you may find it hard to understand if you don't like big crowds. Usually that is because something happened in early life that taught us that packs of humans are bad. But for people raised in big families and who have played team sports and have enjoyed going out to social events, they get energised by packs of humans, just like dogs do with packs of dogs.
Why off lead dog walks are naturally good for dogsThe big difference is dogs are carnivores and humans are omnivores. This means that the dog pack has many facets that make an individual dog happy and fit. Yes the walks make a dog physically and mentally fit, but the purpose of the wild dog (and wolf) pack is for hunting for food and survival. A good pack structure will have a strong leader, and willing followers. They each know their place in the pack and that place ensures survival of all members of the pack as they hunt down their play.
Living in these kind of intense scenarios, daily, really bonds the dog pack so that their social play time afterwards (for dogs anyway) is also highly enhanced. Wolves are rarely lone wolves. Wolves also love the pack (after all its where domestic dogs came from), but they don't play much after puppyhood as there is too much at stake with the chance of fights breaking out and destabilising the pack,. If wolves regularly played in their down time the risk would be too high that they would get regular (and severe) challenges to pack rank status. The play challenges would be so serious there would be high potential for injury that would wreck the hunt.
Dogs in our pack quickly sort out pack status on the walks. And notice I am talking about directed pack walks. It needs to have purpose and direction and flow. We stop to meet other dogs coming the other way, but our pack walk is mostly about exploring the environment in one direction and covering ground, like a simulated pack hunt.
Standing in one spot and throwing a ball continually usually either ends up boring dogs or making them too focused on the ball and anti social with other dogs - the opposite of what pack walks do. True happy and fit dogs rarely occur by accident. The social pack dog is almost automatically transformed into being happy ..