Anything that could potentially make it harder to win for the team without a leaver than before that leaver left should never be considered. It is bad enough the leaver is already a problem for one team.
Why? If matchmaking is fair, then the backfill should also be fair. If a player is better and matched with a backfill of similar rank, then he should still win. Why should a team’s victory be guaranteed, guarantee should come from the player isn’t it, not just some lottery of getting a person with bad internet connection.
I don’t know about you but I don’t want to backfill if it doesn’t mean anything.