I always take with a grain of salt that the chefs are employing some hindsight in their talking head interviews, given they are filmed after the challenge. But I choose to believe that Brooke and Sheldon recognized the challenge from it's use in "Top Chef: Masters" and realized that they were dealing with likely cooking newbies who may turn out to be related to them. Clearly having that many people yelling instructions over walls barely farther away than your average cube space means that noise confusion is a factor along with the shortened time of a quickfire, so few people recognized the voice of their loved one. Also as someone who is really distracted by noises in my workspace, I have some sympathy for Brooke finding Shirley's yelling distracting, although I completely understand why Shirley ignored that.
But these chefs were all very nice to their mystery person. (And Shirley's husband saying this is just like our marriage, I do what Shirley tells me, was the cutest.) So Sheldon likely did suspect that was his wife, and seeing the other loved ones revealed to his fellow chef helped.
I also was fascinated with Sheldon's finding connection between Hawaii and the South as areas with obvious regional influences on their food. (I say this not just because he referenced Hawaii, but that helps.) And yes, having Shirley and Sheldon in the top two is really the best I could expect.
Speaking of hindsight, I think Brooke is right that she does better with concrete challenges. Creating her own challenge by using a combo of things from successful challenges, meant she ran into the editing issue again. And John looks better now that teamwork isn't really required in the challenges. I recognize that, this is the difference between being a chef in the real world and being a chef in a competition. This is the time in the season where Last Chance Kitchen starts to bug me a little. I weirdly, for someone who won't watch it, just want someone who had a weird day early on, or a bad team challenge to fight their way back, rather than the most recent eliminated chef. It's very backwards logic on my part. It isn't that I don't want Brooke in the finals, I do. Of course no matter where they put the cutoff it often is painful, so I will stop worrying over this, and go back to wishing I could eat some of the food.