Also it shows the course maker can be used to create point to point courses.
I was not under the impression it is point-to-point, for me it always seemed like a closed circuit.
And point-to-point Course Maker courses are legally available in the game under the Gran Turismo Rally races (Special Events).
I was bored so decided to map the original track out using the map on that video. It's very nearly a circuit, but not quite. I double checked but this is basically right, I always made sure each piece I cut had a part of the last bit on it to line them up.