Marc,
That is possible. Around here, other than industrial FS type boxes, there are very few metallic cover plates. Most of the injuries cited in the substantiation for this rule were in dwelling units, most likely with nonmetallic cover plates, and there were still a large number of burn injuries. I am only trying to point out what I believe to be a design flaw in the TR devices that results in a false expectation of safety. When this was proposed I fully expected that the design of the device would require simultaneous insertion to open the shutters, but that is not the case, as least with the 2 different brands that I have played with.