The dogs Zeke went up to just weren't interested in playing. I kinda wonder if these people let their dogs play at all. I highly doubt it. I think "play" to them is running in their yard after a ball...which is good I guess, but dogs need to be dogs and that includes play fighting.
I've never stopped my dogs from playing with others when they were pups. They made their own minds up when they got a bit older that they didn't want to play with other dogs. Just because a dog doesn't want to play with other dogs doesn't mean it's owner never allowed it to play.
Having Border collies, they are an obsessive breed who are bred to work, not go up to other dogs to play. Their job is the most important thing in their life and if they do flyball, then flyball is the most important thing in their life. They simply aren't interested in play fighting, they have better things to do and some of them can get quite narky if other playful dogs run up to them and jump on them and bite them in play.
My dogs would go completely nuts if another dog ran up to them and started biting them, even if it only meant to play.

Think about it, would a shepherd want a working dog who only wanted to go playfighting with other dogs? No, he wouldn't, he wants a dog that is dedicated to it's job and that is how Border collies have been bred and they are famous for this attribute. I know that not only Border Collies might show this tendancy.

Like humans, dogs have very varied personalities and this is the case no matter what type of training they get etc...
Not all dogs want to playfight. In fact, many older dogs don't want to playfight. It's more common for young dogs, pups and those not much more than pups, to want to run up and have playfights.
Many dogs might playfight with other dogs that they live with but not want to do it with strange dogs...which is, again, understandable.

Saying all of this, I agree that the club made a lot of mistakes and handled things in an inappropriate way etc...
I also agree that this club is probably not the right place for you if they are too competitive whilst you just want some relaxing fun. The club I went to was more about having fun than being all competitive.

I just wanted to clarify that you are mistaken in thinking those dogs don't want to play simply because their owners never allowed them to and that ALL dogs need to playfight when they don't.