Custom Drops: Mining customized blocks does not destroy mining item (pickaxe)

Craftbook 3.10.1 + Spigot for 1.15.2
When a player tries to mine some block that has edited drops,
Item for example pickaxe stays on same durability as before.

This only happens when append is set to false

my example file:

custom-drops:
cobbledrops:
block: "COBBLESTONE"
drops:
Gravels:
item: "GRAVEL"
chance: 100
minimum-amount: 1
maximum-amount: 1
type: block
append: false

Video: https://gyazo.com/7c3354f6b0004962204499945515e1ff