I took my very first exam yesterday. At one point, we were required to execute a desarming technique against a shomen uchi, and we were allowed to choose to be attacked either with a katana
or a bokken. The only three of us (me included) who chose the bokken failed this part of the test. I suppose that it means that we lacked self confidence to beggin with. Those who chose the katana all said that they trusted the blade to be a strong motivation not to mess up. And it worked.