Prevent matchmaking from injecting players into existing matches

I’m developing a 2v2 island designed for 4 players with teams of 2 players each.
Island settings are Max Players: 4, Team Index: 2, Team Size: 2

Currently, when a running match has fewer than 4 players (either because only 3 players queued up, or someone left during a match), the global matchmaking service adds new queuing players to the existing match as spectators.

However, I want to prevent mid-match joining. Once a match has started, I’d prefer that new players entering the matchmaking queue be directed to new matches instead. Having players join existing matches, even as spectators, disrupts the gameplay experience, new players have not interest in join as spectators.

How can I configure my settings to prevent players from joining existing matches and ensure all newly queuing players are assigned to new matches instead?