Could you get a straight line from IG to that plot of land without going over parts of the park?
The way I see it, they picked the terminal at IG. They picked the terminal at Riviera. Then drew a straight line, and didn't like the path. After that, it's just dragging a point in that straight line to create 2 new straight lines that only crosses stuff they want to cross, which looks like they didn't want it over any of the parks along the way.
They could have picked other routes, not from Riviera, maybe from CBR or direct from HS. My google maps skills aren't up to the task, but starting from IG and drawing a cone shape out that's not to close to France and stays out of the park on the East, and also not to close to the Boardwalk Conference Center on the West. Those would seem to be the limiting factors getting out of IG to anywhere. To my eye, it doesn't look like anyplace in that cone is someplace where you would put a terminal. Which means it has to be a turn station, and it's just picking which terminal to go to then.
I suppose they could have put a double terminal in the HS parking lot, but sending all IG bound guest to HS first sounds sounds like a poor choice for operations.