netigerfan....one of the key things you have to grasp in this game is that it is a game....therefore, the "reality" is controlled by the programmers. Sometimes it does not make sense in terms of real life football (coaching, actual gameplay, player performance, etc, etc), but that is the way the game was set up.
Real life football thinking will get you pretty far in this game, but then you have to add in the limitations (or exploit them) to reach full satisfaction. In this case...you just have to accept that GI is equal to STR. Another somewhat crazy example is the HANDS rating for receivers.... Sometimes its a matter of understanding the definition in terms of how the programmers approached it....sometimes its a matter of just plain weird....