The point is to add opportunity to make blacklist for items which can be placed into crates.
For example, with parameters
"interactable": {
"interactionType": "crate",
"inventoryUnits": 2.0,
"blacklist": ["minecraft:iron_ingot"]
},
players won't be able to place iron ingots into that container. vice versa with whitelist.

Why? This feature offers more ways to set up containers, and gives possibility to create containers designed only for specific guns/ammo/blocks.

This is a feature. Help with debugging, earn some credits, and it can be put in.