At the very bottom of the blockBehaviourConfig is the area for effects, divided into sections (1 per effects). Each effect then lists variables for the various weapon types, and the bottom, you'll find this snippet.
<PiercingDamagePerservedOnImpact>
The amount of damage carried through from block to block, EHP of block hit ignored (Piercing). This is what is applied to Punch.
<PunchThroughDamagePreserved>
The amount of damage carried through, subtracts the EHP of the block and then multiples by this value (Punch). This is what is applied to current piercing.
Of course, you also have <Punch> and <Pierce>, I suggest setting the one that you will be using to true, dunno how the code will handle a mix-match.
To remake the pre0.189995 punch, Go to the Punch section, set <Punch> to true and <pierce> to false, and change the <PunchThroughDamagePreserved> to 1.0 (100%).