Civilians defending their lives indeed cannot be proactive like police officers.
Common sense tells you that when defending your family inside your home, there may be nonperfect situations (i.e. the attacker is not always
directly facing you for a perfect shot through the heart like on a target at the range). Situations might also include a less than ideal shot, "where the bullet must travel a longer distance through a limb or penetrate at odd angles" before reaching the vitals to hopefully stop the threat.
This principle of "nonperfect situations where the bullet must travel a longer distance through a limb or penetrate at odd angles" applies to civilians and LE and should
not be confused
with civilians being proactive like LE are charged with. Civilians defending their lives indeed cannot be proactive like police officers.