3. Also, did you even recognize the threat being presented at this point in the film? Was it clearly shown that Merry and Pippin were even facing what we suppose is Saruman?
As soon as Treebeard says "The White Wizard will know," Merry gasps, "Saruman." Then Treebeard drops them on the ground, they look up, and we see Gandalf from behind. A general viewer would probably realize the potential danger.
I guess they needed that scene based on what Elenorflower said, but IMO they could have ended with Merry's line.