I have experience in racing, cars, computing and lots of other things. Thus I cannot be wrong, misinformed or mistaken in any of those. Apparently.
The fact that the users of THIS forum with an iPhone 4 don't seem to have the problem (that I can recall anyone saying, I may be wrong) must therefore mean that it's a design flaw that affects all iPhone 4s without exception.
Yes, the phone has flaws. No it isn't perfect. But the signal issue is a minor one that probably strikes one in ten phones at the most - probably closer to one in one hundred.