Scourge Arrow:how shaper bow mod "Projectiles deal (20–30)% increased Damage for each Enemy Pierced"

Hello everyone!

I have a SA (Slayer) that works really well.
Here's the POB: https://pastebin.com/UFQXeRbk

I'am wielding a Lioneye's glare atm but i just crafted this bow that i'm going to multimod

But i was wondering how does the Projectile mod works with Scourge Arrow since the skill works in 2 parts. Does the Increased projectile damage works with the pods projectile or just the initial arrow wich pierce automatically all enemy.

Path of Builing doesn't take this mod into consideration so i don't know if it's good or useless.

If someone know how this works or have an idea how it would work, lemme know :)

In the meantime, i'm going to try to unlock some crafting bench mods so i can multimod this bow and let you guys know.

Stay sane Exiles !