Something Strange About T-Rex

I've noticed something strange... Nearly every Tyrannosaurus rex specimen is unique in at least one anatomical feature. Such as Sue has a femur as long as her tibia and had a small skull for her size. Stan has long legs with huge feet but a small body The UCMP Rex has huge feet and short legs The "C Rex" has a big head but a small body, making it is as big as Sue Tyrannosaurus "X" has long legs, a light build, a curved lower jaw and small nares. The Devil Rex has a tibia much smaller than its femur, tiny eye sockets, unusually small arms, big nostrils and strangely positioned legs that are directly under its body, making it very slow. One T-Rex specimen has evidence of Gorgosaurus-like eye crests while no others do Peck's Rex had big teeth and a short rib cage No other dinosaur had any major variance like this, so why do you think this is?