I don't know but what does it matter? The point is that all phones lose some signal strength to one degree or another.
And this so-called problem didn't affect all iPhone 4 owners the same and appears to be worse in areas with weaker signal coverage (something AT&T is known for to begin with.) I know people who own iPhone 4s who have never noticed the problem, and I work with someone who cannot reproduce the problem on his.
I'd say the issue comes from a combination of things and the efforts to push it as a problem unique to the iPhone was misguided at best.
Well it does matter because the whole point of this discussion is to demonstrate that the iPhone 4 has a single major point of weakness that no other phone has. If the 3G or Droid Eris don't have a single spot like that then they don't have the same problem.
Unless you can name any other phone that can lose so much signal from a single spot, then the problem is most definitely not misguided; it still lands squarely on the iPhone 4.