Not exactly. It goes further. While I don't know the specifics of the law state to state as many states now have a form of it, the significance of "Stand your Ground" laws is that it protects a citizen in any circumstance against prosecution where lethal force is used in self defense. They specifically abolish a requirement to retreat in any circumstance when threatened, hence the name "Stand Your Ground."
The courts have always recognized a citizens right to defend themselves with lethal force in the home or in their car when faced with an imminent threat. Laws often trapped citizens because they had to prove what they thought about an attackers intentions (just give them your wallet and you wouldn't have been harmed for example). Then citizens were prosecuted on the decisions they made based on what they should have thought immediately following initiation of the event. Prosecutors argued that they acted before they knew whether the perp had a weapon for example. "Stand Your Ground" makes self defense more objective and less subjective.
This case is relatively unique in that GZ's actions as an attentive citizen led to the confrontation that resulted in the necessary use of deadly force. Had GZ ignored the suspicious individual and went on his way, there would have been no confrontation. But GZ did nothing illegal and should therefore not be responsible for TM's death.
Thanks for the clarification, I guess I was wrong. I’m in Ohio, and we have “castle doctrine” which I thought was the same thing. Looks like we need SYG...