I think you are likely right. This does seem to be how all of the lines work for the top-tier attractions. I think the only exception to this was on my most recent trip. The line for Tron at Park close said 135 minutes, and based on what I know of that line and speed at which it moves, it looked like it was probably pretty close to accurate. They even had switchbacks set up on the bridge leading inside the building. Usually I’ll jump in a line even if the wait time is high, but that one scared me too much to try it. It might not have been 135, but it was easily 90. I’m hoping that won’t be the case with Guardians, because getting in line at Park close is my other favorite trick for an extra ride on fun things.