For example, when you want to play Build battle in another server but your friends don't know the IP, what's the problem on telling the IP?
Sure it seems harmless enough from the player point of view, you just want to play another gamemode with someone else, and you fully know you'll be just as active on this server as you were before. Maybe even your friend. But from a business perspective, they have a player who is literally telling other players to leave the server and go on another one. That's bad for them. Not to mention the fact that the other players might just prefer the other one and stop being active players here.
And this "bending of the rules" that you're suggesting just sounds like a loophole. It can easily be abused, and since its in private message mode, abusers of this will probably be getting away with it.
I mean, they could allow it and all, but it wouldn't really be a smart move on their side.
Again, this can easily be done if you have discord. It's really something which you can leave on at all times and easily add/msg people whenever you want. I play on a pretty low-tier laptop, and leaving it on all the time doesn't affect my performance in any way.
