While I agree that the guy shouldn't have just jumped in like he did (although I kind of missed the fact that he is German; my best friend is from Germany and can be very rude by accident), making excuses for your horse is neither in your best interest or her's.
I hate riding dirty stoppers, and that is why when I am teaching a green horse to jump, I don't care if the grid is not set up for their stride. When I was schooling a butt to the sky, 15 hand greenie to pop over grids, I had him take it whether or not it "fit his stride". Even though they were just cross rails and small verticals, it helped him, and certainly did not sour him. I'm going to do the same thing for my new horse.