Shapes describe the physical path that a vehicle takes, and should match the real-world roads, railways, and similar features on Google Maps satellite imagery.
Shape points do not need to match stop locations. And stops do not need to be connected to the shape with short segments. Google is able to recognize stops correctly that are up to 150m away from the shape.
Please check the Validation Report for "Stop too far from shape" and "Stops match shape in wrong order" warnings that indicate potential shape issues that need to be fixed.
Shapes that have lots of looping or inlining should have values for the field
shape_dist_traveled in both stop_times.txt and shapes.txt. A common value to use for the
shape_dist_traveled field is the distance from the beginning of the shape as traveled by the vehicle. Please note that this differs from the straight line distance; the straight line distance doesn't represent the actual path of the vehicle through the street network.