I often hear sportscasters talk about some athlete having his game face on. It means a look of concentration.
What does concentration look like? To most people, it means a degree of extra tension in the face. If your face is not free to react freely to the moment, then your options have narrowed, your thinking has narrowed, and your emotions have narrowed. I can’t see how this is helpful in any endeavor.
Concentration is not helped by scrunching and tension. Concentration is helped by the letting go of unnecessary tension so that you are more free to be in the moment.
From UrbanDictionary: “Game face means “a confident swagger you bring out when you are about to get ready to tackle something difficult, or when you are about to take on a challenge. Or when you are getting ready to get down to hard business.”