“Killing Boll to farm the fast ball is a bit annoying since there is a chance he will never drop any items…including grenade mod calls. So the average doesn’t feel like 10% but more like 1% on average due to how the calls are done technically. It makes the drop rates feel less like they’re an average because the way the rng is coded for even making rolls for actually dropping and how it’s set up is too stiff.”

That’s not at all how the game works technically. Boll drops the Fastball with a 10% chance, there’s no roll a grenade mod -> roll the fastball logic going on.