Based on a related question, where Eat Sin was quoted, I noticed something rather… strange.

Eat Sin (Sp)

At 1st level, as a free action, when the sin eater inquisitor kills an
enemy, she may eat the sins of that enemy by spending 1 minute
adjacent to its corpse. This provokes attacks of opportunity. The
inquisitor can rush this ritual, performing it as a full-round action
that provokes attacks of opportunity, but she only gains half the
normal benefit (see below).

Eating the enemy’s sins heals the inquisitor of a number of hit points
of damage equal to 1d8 + her inquisitor level (maximum +5). The enemy
must have been killed by the sin eater within the last hour, and it
must have had at least as many Hit Dice as half the inquisitor’s
level. The inquisitor can use this ability once for each enemy she
kills. This ability has no effect on mindless creatures or those with
Intelligence 2 or less.

At 5th level, the healing increases to 2d8 plus her inquisitor level
(maximum +10); it increases to 3d8 + her inquisitor level (maximum
+15) at 9th level and to 4d8 + her inquisitor level (maximum +20) at 13th level.

In some faiths, this “eating” is a purely symbolic act, while in
others, the inquisitor must eat a small amount of food and water as
part of the ritual. A few extreme faiths actually require the
inquisitor to eat some of the body of the slain enemy.

At 8th level, when a sin eater eats the sins of a creature that would
rise as an undead (such as someone slain by a shadow, spectre, or
vampire), the sin eater may choose to accept 1 temporary negative
level to absorb the taint in the corpse, preventing it from rising as
an undead. This negative level can be removed with the appropriate
magic, though it automatically expires after 24 hours, and never
becomes a permanent negative level. At the GM’s discretion, this
ability may prevent a ghost from using its rejuvenation ability.

The first two bolded parts pretty much insist that you as the inquisitor must have killed the creature and sound pretty good per flavour, you kill them and then absolve them of their sins. However, that would make the 8th level upgrade to Eat Sin almost completely moot; you can't eat the sins of somebody killed by a shadow, spectre or vampire, unless -you- happen to be the shadow/spectre/vampire that killed the corpse.

Is this how the feat was intended? Can you only eat the sins of a creature you yourself have killed?