Let's imagine a situation where the tournament organizer unexpectedly comes up with a scheme for the Fortress Battle, requiring exactly 12 players. How do you find the other two? Either conduct another selection, invite participants for other merits, or take the next in line from the Open Fortress Battle. The problem is that there is no single regulation for the Fortress Battle tournament, clearly outlining the rules and the number of participants.
The correct way to present an expansion of the Fortress Battle:
"Guys, we've been thinking that it would be nice to expand the Fortress Battle a bit (here, explain the reason), is anyone against it? No? Okay, then we'll add two more players based on rating/voting by participants/results of the Open Fortress Battle/wildcard from the organizer, is anyone against it?"
That is, it was necessary to: 1) ask the players 2) decouple the expansion of the Fortress Battle from the results of the Open Fortress Battle. And certainly not to interfere with such a delicate moment with dubious ideas like forcing Rebel and Cobra to finish their match as part of the Fortress Battle.