Except that common sense is often wrong (like your anti water spreading plugin), so it is perfectly fine to ask. BTW, you are abusing bolds a bit.
read the docs/source code yourself. https://github.com/PocketMine/Pocke.../event/inventory/InventoryPickupItemEvent.php
read the docs/source code yourself. https://github.com/PocketMine/Pocke.../event/inventory/InventoryPickupItemEvent.php