Gruber's actual comment: "I don’t know if this signal-degradation-in-left-hand thing is really a widespread problem or not yet, but it’s not reasonable to tell people not to hold the phone this way."
He's mentioned that neither himself or anyone of a number or friends he's asked has been able to reproduce the problem. How could he possibly write exhaustively on the topic at this point, given the lack of information and personal experience of it?
http://daringfireball.net/linked/2010/06/24/iphone-hold