[jsr]

Yeah, sounds like a thermal pad. It's not electrically conductive, so no worries about shorting things out. Ideally, the thinner the pad the better, but manufacturing tolerances for the plastic case (and thus the mounting depth, placement, etc. of both the PCA and heatsink) and for the heatsink may require 1-2mm of tolerance to ensure no interference in fit. That and perhaps they did think about the possible physical stress from an impact as I mentioned (maybe, I don't know). Regardless, the thermal pad is better than most electronics where the heatsink just sits atop the PCA with air in between to act as a thermal transfer medium (and radiation is not nearly as effective as conduction through a thermal material). I personally wouldn't worry about the design. Those thermal pads work fine in most environments except in vacuum.