True Overall™ is a deep neural network model created by ShowZone. Since it is created via a neural network, extremely unique scenarios with attributes that would typically not be seen in-game may generate odd or non-standard results.
In addition, if you are formulating the True Overall of a CAP hitter, it is recommended to place zeros for the pitching attributes instead of the default 30 base attributes (the neural network model will start to rate you like a 2-way player otherwise).