It was because the P-47 was a 'Pursuit' Aircraft?
http://www.wpafb.af.mil/museum/ind/pind.htm
USAF Museum Pursuit Aircraft Index
Curtiss P-6E "Hawk"
Boeing P-12E
Boeing P-26A
Seversky P-35A
Curtiss P-36A "Hawk"
Lockheed P-38L "Lightning"
Bell P-39Q "Airacobra"
Curtiss P-40E "Warhawk"
Republic P-47D "Thunderbolt" - Razorback version
Republic P-47D "Thunderbolt" - Bubble canopy version
North American P-51D "Mustang"
Bell P-59B "Airacomet"
Northrop P-61C "Black Widow"
Bell P-63E "King Cobra"
Fisher P-75A "Eagle"
Lockheed P-80R "Shooting Star"
Snap B73, with knobs!
SS