Smile

Recently while watching a Cricket match, one of my friends said,
"McGrath always keeps smiling. Even if he gets a four hit on his ball, he smiles. It is like he means to say that 'Okay you have hit it this time, but you will get out anyway'. Such an arrogant person he is."

Now I don't quite get this. McGrath might be arrogant, but I don't understand why his continuously smiling is being misinterpreted that way? Why is not being taken that he means to be cheerful in all odd conditions?

To continue watching match and since others were in agreement with this view, I had to stop arguing there, but I still din't get this :)