This might have been lost in translation to Chinese: Penetration of the Soul (warp_attacks_rending) is the Psyker talent which is bugged. Penetrating Flame (burned_targets_receive_rending_debuff) is the weapon blessing which works as intended.
the psyker_warp_attacks_rending buff has a proper warp charge percent threshold check for conditional_stat_buffs_func but the start_func effectively does nothing.
You will likely need a proc_func or a update_func that actually sets a variable or returns a value that can be used in damage calculation.