Some questions from today's landing.

I watched the landing today on the Nasa web video feed. Two questions came
to mind.

Houston would often acknowledge instruction readbacks with "That's a good
copy", or "That's a good readback". Standard aviation talk would be
"readback correct". I'm curious why they went with different wording.

When the shuttle was on final approach to the runway, there was a head-on
view shown. I couldn't quite tell, but it looked like the split rudder was
open. Do they use that in flight for speed control like an airplane might
use flaps or spoilers, or it it just used after touchdown to reduce rollout
length?