ARRANGED TEAM CHAT SECRET ENTRANCE?

So whats with the huge group chat when I drag someone from my friends list into my lobby queue's arranged team chat?

In other words queue up and in arranged team chat, drag a random friend from the friends list into the spot where the players names are and another group chat opens up....

Im pretty sure this is just a public group but why is that a way to get to it? Is it a glitch? Is this the only way to get to that type of group chat?