That is odd because I was fussed at long ago by an actual Italian bicycle manufacturer, not a rep but the main fellow himself, for having my handle bar lower NOT parallel to the ground/top tube (then all were level top tubes). According to him it was virtually Canon Law and that the lowers be level to the top tube and that anything other than that was heresy and an abomination and possibly a serious sin against Italia. And according to him my brake levers were incorrect because they should be set such that a straight edge along the levers would intersect the bottom tip of the lever. So I do not see that either are correct.
Would not the shape, depth and curvature of the bar have a bearing on how it should be installed? Brifters are so huge and bars today are so shallow, something has to give somewhere.