What an excellent post.
You bring up so many good points. First: Why do people push their dogs? I think ego is part of it and impatience the other. Everyone wants to have the youngest dog getting an orange ribbon in the Masters Stake. (Maybe if Entry Express did not list the dog's birth date, that would abate somewhat. Maybe not.)
Second: People have to understand their game and respect it. I believe my 7 year old dog couldn't do a 400 yard blind on her best day and it would have been stupid to try to train her to do it. I think Rocket Dog would LOVE, LOVE LOVE to work on long blinds. Hoo-HAH!!! By that I mean, I think I could begin stretching her out and slowly introducing more and more factors. She would be a lining fool, given the chance.
But therein lies the secret. Rocket Dog is in the HT game and lining is less of a big deal, whereas quick, exquisitely precise handling is absolutely necessary at the highest levels (Master National quality.) All the factors, all the suction and sudden-death-long-walk-of-shame dangers are going to be within 200 (maybe 250) or so yards of the line. So, that's how we roll.
But wow... putting pressure on the dog to do something you have not worked on with him/her... not good. I don't know if you've ever watched Mike Lardy's Total Retriever Training, but he has an excellent segment of it where he ran a FC on a triple with two retired guns. The dog went for the memory bird, gave a cursory hunt and turned toward the bird he'd just picked up. I think Lardy called it a "flagrant violation" or something like that. He came down hard on the dog with a big whistle, and some burn, and explained to the camera that for THIS DOG such a switch was a major felony. The dog knew exactly what he was getting burned for. Then I think he handled the dog to the bird.
On the other hand, another dog went for the bird he'd just picked up because the roll of the ground was such that by giving in to the factor (downhill slope) it pushed him into the old fall. That was confusion. No burn. Just handled to the mark.
Then there is the issue of letting the dogs get away with stuff (ignoring a whistle) and NOT dealing with it appropriately. But their dogs shouldn't have been put in a position where they where this was a near certainty. It's like refusing to allow your dog a chance to succeed. We ran a blind yesterday that was totally counter-intuitive for Rocket Dog. She had just picked up some blinds in the field on one side of the road. Then I turned her around, had her run up the embankment and onto the road, to cross it on an angle (ideally) and then take an acute angle to the blind some 100 yds away. Well... she got in the middle of the road and you could tell she was totally perplexed. I'm sure she thought I'd lost my mind. But I just moved up on her and helped her. I didn't try to burn her across the road, down the embankment and into the next field.
I concur with what you did with your youngster. You had nothing to gain leaving her on the truck, and a lot to lose.