If you sat on the e.g. right going up and on the e.g. left coming back you saw the very same trees, just in a different order. To see both sets of trees you need to sit on the same side going both ways: e.g. right side going out and right side coming back.
Or at least that’s true if you reckon left & right versus the train’s direction of motion. Which is the usual convention.
As I recall, I sat on the west side on the outward leg and the opposite, or east, side on the return. I think when you’re talking about the view it’s a reasonable thing to say.
It’s moot anyway as the OP isn’t takimg the trip.
To see both sets of trees you need to sit on the same side going both ways: e.g. right side going out and right side coming back.