Directly from
GW's site listing for the Sisters Repentia:
Confession and penance are part of s Sister's everyday existence, those who fall short of the rigorous codes may find themselves banded into groups and led into battle in an attempt to earn redemption.
This is different from the listing for Penitence Engine with refers to
heretics
and says
that only in death can forgiveness be forgive.
So
IMO it looks like Repentia can earn redemption without having to die. But I'm not that familar with the
SoB, that just what I get out of
GW's descriptions.