In Q&A they seem to be glossing over or ignoring the whole "if you bridge the gap the signal drops" issue (demonstrated here with a paperclip http://www.youtube.com/watch?v=kgouzUMlQpY but as I understand it your finger will do the same thing). At least when asked somewhat directly, one engineer gave a complete non-answer.
What you see there is a drop of between 6 and 22dB (from four bars to one [+]). Gripping the iPhone will reduce the signal by at most 24dB. I don’t know whether they don’t acknowledge that. They showed a “X marks the spot” slide. That, to me, seems to be a pretty clear acknowledgement that merely touching that spot weakens the signal. [+] http://www.anandtech.com/show/3821/iphone-4-redux-analyzing-...
That is ridiculous. You aren't "covering the antenna" when you cover that spot. The antenna is the big strip of metal above that spot. Instead you're upsetting the profile of the antenna, which is entirely different.
The presentation was incredibly deceptive and flawed.