Yeah, this seems like the case. Not only does Trial Mountain not have any circuit lights on the side of the track, but this would also explain that cloud shot during the first 2020 trailer. The clouds were moving rapidly, but the shadows were static. It makes sense, because I don't think Polyphony would let players drive around a pitch black Trial Mountain. It was the same in GT5 and GT6.
Now the question is: Why the hell did they not add circuit night lighting in the overhaul? I was one of the people who wasn't happy with how much they changed the track. Why would they remove most of what made the circuit stand out from the rest, but skip out on adding night track lighting?