That's funny. I hook up before and unhook after they go on the tires. I've never had any problem up to this point. I guess I need to read the directions more often. Seriously, though, I don't remember seeing any such paper in my box at the time I bought it, but I could have missed it.
It still doesn't make any sense to me that the X-chock could allow the wheels to roll so I've got to use a separate chock, but is designed to prevent the slightest wheel movement. I mean, that's the whole idea of how the thing is supposed to stabilize the trailer, from what I understood. I think that piece of paper in the box must be there to save them if they ever wind up in court over a runaway TT.
It's a concern to me if these "chocks" can't chock reliably, and that's what I'm using them for.