A few people have reported that, with the new matchmaking system, it is no longer the case that Friends Queue needs both players to be in Friends Queue, but one player to be in Friends Queue, and the other player (who is on player 1's friend list), to be in Any Rank Queue. If both of these things are met, the two players can queue into each other, allowing for people to unintentionally snipe other from Friend's Queue.

This is slightly different from the old method of sniping, where player 1 and player 2 are friended, and player 2 and player 3 are friended, and while player 1 and 2 want to get into a match in friends queue, player 3 is also in friends queue (maybe for their match, who knows), and matches with player 2. This is basically unfixable in my eyes, because it would require the game to realize the intentions of the players, but perhaps it could be done by prioritizing recently met or smth.

Anyways, the point being, Queuing in Friend's Queue is no longer limited to those who are even to match with other friends, but anyone on your friend list.