Maybe the editors just dropped the ball there (or didn't really feel it was important). Editors have been known to drop the ball.
At some point in the next few hours, watch ANH and fast forward to the part where R2 took off in the night to find Obi-wan. Luke asks 3PO where R2 is, then runs out of the building. You see how fast Luke is running, and how fast 3PO can walk. Luke runs out of the hut and out about 10 paces, and 3PO immediatly appears next to him. I noticed it years ago, and it always makes me laugh.
I do suggest you check it out, if you hadn't noticed it already. Trust me, it's pathetic! 😕