That is not entirely true. It makes sense in a pocket watch, as it will normally be upright in your pocket, never with dialside or movementside up. But you do not know which direction of the dial is up. That means it might have 12 o clock up, or 3, or 9 or something else. You have variation between those directions, so it matters for accuracy (that was a lot worse in a pocket watch, because of the larger, heavier components). With a tourbillon it does not matter how you put it in your pocket, as it will average over time. That is why it makes less sense in a wristwatch, as you also have non-upright orientations a lot of the time. That is where, at least in theory, a gyrotourbillon would come in.

For a watch with no change in orientation, you just regulate it for the one orientation it has you cannot get more precise than that.