This only affects "DistancePointToPlane()". The orientation of the grid pattern that visualizes the plane is arbitrary inside the plane. Inside a plane there is no preferential direction. For some planes or some plane rotations the grid pattern orientation may look unnatural. Provided you know how your plane will be oriented most of the time you can mitigate this by specifying the preferred grid orientation. The preferred plane pattern orientation vector works best when it is roughly perpendicular to the plane normal. The more similar those two direction are the more it can look unnaturally rotated. So if you are working with planes that lie flat on the ground then "Vector3.forward" or "Vector3.right" may be good choices. If you work with planes the are rather vertical then "Vector3.up" is a good choice.