Hi blaupuma, as far as I can tell just from the photo, the photo was taken during installation, as you can see that adhesive has been combed at the back. If this is the case, you can also see that no leveling system is being used. You don’t necessarily need one, but you can’t get concave tiles (which 60x60 always are) to the same level at all four corners any other way. I’m glad you were lucky and found a good tiler, and as I said, maybe it’s not his fault because the tiles’ calibration value (usually indicated with a code on the tile package) is not particularly good. Then he’s doing the best he can with it. I only saw a non-accurate grout pattern (related to the grout line) in the picture and no leveling system or edge insulation strip. Those were three points that didn’t make sense to me at first. There were tips about the edge insulation strip, and the other points have more factors that we don’t know.