I used to think the same thing still I started playing around with Opinels. If you have a bench vice, $15 and some idle curiosity, you can try your hand on creating blade play. The blades are so thin and flexible and the joint is so tough (steel collar, not pinned bolsters) that you'll work harden and snap the blade before you'll damage the joint. You *can* bust the wood in the joint if you twist them hard enough, but that's pretty hard to do. I gave a #8 to a buddy who works as a carpenter and dared him saying I didn't think we could break it. He's had for 6 months and hasn't been able to bust it. Regularly uses is to open paint/putty/tar cans. The blade bends but snaps back. Zero blade play. While interesting and sort of fun from a "can you bust it" point of view, I thinks it unrelated to the vertical play issue.