I'm trying to get mobs to drop all worn/held equipment on death, but can't get it to work. Specifying the appropriate tags with "nbt" seems to have no effect.

[
  {
    "onjoin": true,
    "result": "allow",
    "nbt": {"HandDropChances":[1.0f,1.0f], "ArmorDropChances":[1.0f,1.0f]}
  },
  {
    "result": "deny"
  }
]

I've tried modifying most of the other tags as well, to no avail. The only thing that I have found to be modifiable is Attributes.

Is this a bug, or am I doing something wrong?
Thanks