Partially, I think that because SO many perpetual calendars (UN, Moser & Cie., and some PPs excepted) use symmetrical 4-subdial layouts, this design subliminally whispers "tri-compax chrono," not "QP," to me. From a strict design standpoint, I also find, ironically, that the empty real estate below 12:00 leaves the 3-6-9 subdials looking crowded in the lower portion of the dial. Finally, I think there's a part of me that wants a complicated watch like a QP to look complicated (pace, Moser & Cie) - or at least more complicated than this.