Summary: Using the /kill command with entities will ignore Data Tags you use with the entity. In this instance, I am trying to use the /kill command to kill Baby Zombies as shown in the screenshots.

How to Reproduce:
1. Find a mob you can use /kill on.
2. Use the /kill command in this format: /kill @e[type=<Entity>] <Data Tag>. Using this format: /kill @e[type=<Entity>,Data Tag] Will return this value: The entity UUID provided is in an invalid format.
3. After the [type] TSA, use a Data Tag that will only select that mob with that Data Tag.
4. Press enter, and the command will kill all entities of that type, because it ignored the Data Tag inputted.