Wow, that's messed up and definitely a miscarriage of justice against your friend. I don't have a good answer for that really, La. also considers the vehicle as an extension of the home. Louisana law can be weird at times, and sometimes seems contradictory(and is) to common sense. We are gun friendly, but defensively selective at times, we are economically friendly, but have odd tax structures, etc.
I think Louisiana wants to strike a balance between justified shooting and property based homicide which would explain the difference to me. Personally I've seen some very bad tresspassers in my time, the type that seemed to want to fight to defend their tresspass, and while I don't think it's worth killing over it is an aggressive situation. If someone breeches the homestead it's automatically assumed a threatening action under our laws, residents of the home are under no compulsion to flee, on the property we may still stand our ground, but may not initiate lethal violence unless threatened in some way, that includes open and standing structures not connected to the home.