He's commenting on statistics. It's like how someone I game with really wants to get an exotic bounty, so he tried turning in 5 bounties at once. Does it help his odds turning them all in at once? No, but if he does it that way he feels like he has a better chance. He's not talking about guaranteeing, he's talking about playing the odds by cleaning up all the enemies. Does he have a better chance? Statistically, yes, but not because of where the enemies were found, but because he killed more of them. Just like you in crucible. Does it matter your placement in crucible? No, but you've played a lot of crucible. Each match increases your odds.