Well, if you have the same fuel, same tires, same track, same conditions, you should hit that speed, right? Or at least within a really close margin. Same thing with the MPG on the sticker - you recognize there are situations where you aren't going to hit it, but if you are running the same conditions, you should expect to get the same results.But much like you can't get a Bugatti Veryron to it's top speed on any old road, you can't expect a variety of motherboards and cooing solutions used for these survey results to give you a clear idea of what is actually limiting the boost clock, here.
Sounds like that isn't the case here - people are using same motherboards, same BIOS, same cooling, and aren't getting the same results.
I think what we are seeing is just the auto-overclock (PBO) is really good at getting to the limits of the silicon, so you are getting the most out of your chip. It's just what is printed on the box is what most people expect to get, and AMD printed a rosy estimate on the box, not a minimum baseline case.
If AMD had printed 4.4Ghz Boost, and some people were seeing 4.5's occasionally, everyone would be overjoyed and estatic, and those that "only" get 4.4 wouldn't feel like they are getting cheated. Instead, they printed 4.6, because they got one sample in a lab to hit it and they were afraid of Intel's 5.0, and now everyone feels like they are getting gypped. Even though the product is no different, and the results are not different. It's a marketing plunder.