I used to be one-removed from the Tech Writer. I developed training for the user on the software product. We too, need to be in the loop. I test each "lesson" and can find "bugs" in the software AND in the documentation. On a complex software product I discovered a problem when I tested my training materials with 12 simultaneous users. The system froze! It was discovered (much later) that each software developer had both a client and a server on their system while testing -- they didn't notice that the software couldn't run with a single server and multiple clients !

Pet peeve: Too many User Guides simply state, "The Widget button sets the Widget." without describing the result of "setting of Widget" or in what situations you would want to do that.