I'm still skeptical until we see a video of a known entity reviewing the unit in hand, preferably at a Gamescom or at an E3. And one that isn't a flash of a video for two seconds of the unit (tethered to something) and the rest people walking around shaking hands and talking to each other.
Is it round the back of the unit though? Cos I didn't spot it during the assembly, and I've not paid close attention to the back of the unit. I'm pretty sure it's not on the front. Also, unless the person using it has very small thumbs, it looks kind of a large switch to go into a handheld unit.