greek dude, let me try to use an analogy here.
Suppose I watched a lot of baseball, and made an interesting observation. My observation was as follows:
The fastest pitches tend to be thrown by those players who are wearing black socks.
Assuming this observation is sound, it certainly requires an explanation.
Here are some possible explanations:
1) It is pure statistical fluke. There is no relationship whatsoever between sock colour and pitch speed.
2) The vast majority of players happen to wear black socks. It is therefore expected that the fastest pitches will happen to be thrown by those wearing black socks, since there is a massive skew in the initial distribution of sock colour.
3) Perhaps black socks absorb more heat, and warm the feet more, allowing for better foot control.
4) Perhaps there is a correlation between athletic prowess, and taste in colour. Perhaps those players who are stronger throwers also happen to prefer dark colours.
5) Perhaps there is a cultural confound - perhaps certain cultures prefer dark socks, and those also happen to be the cultures which have a long history of baseball.
The important point here is that if someone were to respond to this observation (and the proposed possible explanations) by saying:
"dude, professional baseball is not indicative of real performance. These players are highly trained, highly selected, and many use performance enhancers to increase their pitching speed"
this would
not explain the difference observed.
Similarly, if my observation in porn is sound, then the
difference requires an explanation.
Here's another example of a cumshot you will rarely see produced by a circumcised male:
http://xisty.info/claudia_bg_hd01/vids/4.wmv