Urban legend. During keynote he explained that every other manufacturer have similar problem, if you grab phone with your whole hand (which is/was fact and Apple did researched it with most popular phones during that day). He also said, that there was software bug, which was removed in next iOS update. In statistics, iPhone 4 had lower antena problem ratio than iPhone 3GS (also shown during keynote).
In the end - everyone who had this signal strength problem, was able to return phone. Everyone who decided to keep it, would got free bumper.
Seriously, what else Jobs could do? Don't want it - ok, here is your money. You want to keep it - ok, here is your case for iPhone, keep in mind we did solved software issue and remember that every other phone hold in wrong way, may cause such problem.
This is not same situation at all. Here if you have bent iPad, you can return it only in first 14 days. What if I bough it for Christmas gift, two weeks ago, cause I don't want to buy in last second? Should I open the present, cause, for Apple new device could be bent out of the box?