Twitch added a way to merge Twitch chats through Shared Chat. If you trigger a button with Twitch Chat and use Pull Trigger Value, there's nothing to currently differentiate the messages in a Shared Chat (it looks like they're all coming from the same channel_id).
This is different than using Join Chat and parsing out "from Channel ID" as that is two seperate chatrooms. I think Twitch somehow relays the message between all the shared chats into one another for Shared Chat.
The use case here is to be able to differentiate messages from diff channels during the Shared Chat experience, without using Join Channel. The messages will show up twice during Shared Chat if using Join Channel due to Twitch's implementation.