No, it merely means you don't have to turn and run when attacked. The idea is if you're the good guy then why would you have to be the one with the burden of giving ground? In such a case you could quite literally turn out to be the "bad guy" not because you weren't faced with danger but, in somebody else's opinion you could have, you know, tried harder to get away. Anything where anybody is getting killed is messy business but consider this; if an intended victim is actually going to have not only defend themselves from an attack but then have to defend themselves from prosecution for defending themselves on whose side is the law more forgiving...the attackers or the attackee? Is that really the side you want given the benefit of the doubt?
Having stated the above I really don't like it's application (as I currently understand the evidence) with the particular case in question. Specifically, the use of lethal force when "standing your ground" rather strongly implies you're doing so against an overt threat, don't you think? Shooting a kid holding a bag of candy in an encounter where the shooter appears to in fact have initiated a hostile encounter pushes even the most lenient interpretation of SYG in my estimation. I don't think there's room in SYG doctrine to allow for someone to go looking for trouble and then fall back on lethal force when they find it...much less when that level of force is used against an unarmed person. It may only be a personal observation but I've never liked the instigator-turned-victim defense.