David Beckham as a measuring stick

In a study done by the University of Manchester in the UK, new LA Galaxy star David Beckham is used to compare human foot speed to that of a Tyrannosaurus Rex. Why do I find it odd that: 1) Anybody would care. 2) That they would use David Beckham as the human in question. He is certainly known for his soccer abilities, and I'm not quite sure why this is bugging me so much, but why wouldn't they use someone actually known for being quick, like, say, the world record holder in the 100 meter sprint?