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.
I was wrong originally, the issue seems to be in the scripts/utilties/attack/damage_calculation.lua file in the _rending_multiplier function. The warp_attack_rending variable is never even added to the rending_multiplier variable which is returned to calculate the rending multiplier for the final damage calculation. Please fix Fatshark this is a 20 second fix to your code.