Why is a 4 or 5 man group getting not grouped players 5% of the time an issue?

I dunno, but if I told you that 1 in 20 of the games you played was going to have an AFK on the enemy team, but only if you que w/ multiple people (and if you que solo then 1 in 20 games you're gonna have to play 4v5) I bet you'd say there is a big advantage to that consistency.