It shows that they know someone whom they can invite to seed community.
This level is less about attacks (although this attack is harder because it requires an accomplice) and more about encouraging honest people to use the “already know” level correctly at least once. If we care about connection confidence levels at all, we need to encourage users to use them in the way that we intended.
I think we might get better results if we ask someone to bring a friend to a call rather than send a friend to a call, because it requires some coordination. Otherwise, you could be lazy and fulfill the requirement simply by making random “already know” connections to everyone you find on discord. If the “already know” connection must happen in a group connection, then you should try to use it correctly, otherwise you run the risk of the other person marking you as “just met,” since that’s what they’ve been instructed to do. It’s easier just to actually bring a friend. Sure, if you have no friends, you can make friends with someone on discord to fulfill the requirement. Coordinating with someone to join a meeting with you sounds more like friendship than spamming out connection requests and hoping someone will connect. I think many people will find bringing an actual friend to be the path of least resistance, which exactly what we want.