Due to the current nature of the mod. I'm unable to kill only untamed rats which is troublesome on a server when I am trying to debug. If you could simply add a tamed NBT tag, or set the owner NBT to nothing for untamed rats, that would be nice.

Tamed rats have been split off into their own entity now for performance reasons. Wild rats still fall under the namespace rats:rat and tamed rats use rats:tamed_rat