The dogwalk is definitely one of the contacts that give advantage to the toy dogs. The board is wider for them than it is for the bigger dogs. So they can fly across, where the big guys need to slow down and be more careful.
I think you were wise to listen to your dog. Perhaps you could try a different sport he would like - Rally or even tracking, for example.
The odd thing is that when my Golden watched as his “girlfriend”, the GSD, fell off the dogwalk, it blocked him from ever doing that again, although he’d successfully navigated the dogwalk before. But, the GSD got right back on and was the star of the dogwalk thereafter.
My Golden was having none of it. Once in a while he would lose concentration and successfully navigate the dogwalk, but then it was like one of those light bulbs went off over his head, and he thought, “Wait a minute. I don’t do dog walks.” And, he would balk the next time he was asked to do it. Very annoying.