It shouldn't really matter, I guess you would end up with some cuts on the edges, and maybe that is a valid reason to do it the way they did, the edges may be too sharp if you had to cut some, here is a quick sketch of what I was thinking... (Blue pieces from sheet 1, green pieces from sheet 2, cuts would be where the green ones are going over the edge... keep in mind, this is rough). Even if you had to cut the pieces on the ends, the tile guy can take them off of the sheet, and flip them around 180 degrees so that the cut side is facing into the mosaic and wouldn't create a sharp edge. If your spa ledge measures to a whole inch dimension, the only cuts should be the ends of every other green piece at the bottom of this, the others should line up on the edge of the spa. Again, I saw some like yours in a google search, so this may very well be the way it is done as a standard. I just know that my tile guy took a lot of care in making sure that he didn't have to minimize the cuts on my tile.