But we don't know what the banned people did, some of them could have been using a public LFC, others could have been using Pokemon cheats online.
It's not smart to tell people they are safe when we don't know this is the only mechanism Nintendo uses to identify. We should really try to get a better picture of how the un-banned vs banned systems differ besides this.
For the love of my Floette, no one is saying that this is the only way to get banned.