With the Roland Z stand that Ray posted a picture of, I'd say it could go either way, since there's only one cross bar and it's high up enough that it shouldn't get in the way of your feet or knees when using pedals.
But in the picture from On Stage, the lower of the two cross bars might or might not get in the way of pressing any foot pedals, depending on how far forward or backward the pedals are placed and whether you're sitting down or standing up.
As far as the second tier, I'm not sure but I think the second tier can be attached to either side, since it should just be a question of removing the plastic caps so you can slide the feet of the second tier into the holes.
On a same-but-different note, I'm currently using a pair of double-X stands, and at one time-- when I had just one X stand-- I used to set the stand to its tallest setting, then turn it on its side so I could lay my keyboard across one of the "top" bars and one of the "bottom" bars. Fortunately, the top and bottom bars were at the same height as each other in that position, so the keyboard wasn't lopsided, but the bottom bar was a little longer than the top one. The reason I turned it on its side like that was because it was actually a little lower to the floor that way than if I'd set it to its lowest upright setting. That made the keyboard easier for me to play, because at that time I was sitting on a "comfy couch" in the living room, so I was a bit lower to the floor than if I'd been sitting on a piano bench or "hard ass" chair. Now I've got my keyboards set up in my bedroom and am sitting at a proper height from the floor, so I have my X stands turned upright! Conclusion: Whatever works best for you is the "right" way, even if it's the "wrong" way.