Under traditional self-defense law, a defender could still be convicted of killing an attacker, if there was a safe avenue available for the defender to retreat down.
For the most part, this was viewed in a very generous way to any potential defendant - if the attacker might catch them, that was held as good enough.
All SYG does is remove the necessity of checking to see if there is an avenue for a victim to flee down. Nothing more. Under an SYG law, the defender is not required to seek an avenue of escape before defending themselves.
(Btw, if anyone wants to provide better pictures, go ahead.)