I used to wonder if with the segmented bridge set, the turbo was originally intended to be directly behind Kirk's chair but perhaps they changed it for a more visually interesting bank of computer screens.
That reminds me of something F.J. said in a 1982 interview:
But take another type of error which is a major mistake. There are not military vehicles, to my knowledge, that are designed with the commanding officer positioned so he sits with his back to an exposed entry. Yet the captain of the Enterprise sat with his back to the elevator. The reason being, that was where the action of the episode was coming from, and that was the camera angle the producer wanted.
In order to do this, he was shooting at a 36-degree angle to the captain's station and the bridge, so he could include the screen over to the right and the elevator over to the left. When you come to the layout of the bridge, because the elevator is on the centerline of the Enterprise in its external views, you discover the bridge is skewed off 36 degrees from the centerline. But no ST fan ever put these two things together, you don't see it until you try to make an actual layout of the starship.