It could also have to do with the 630 and to make room for the menu button on the face. If the 630 was semi-round, and nothing else was, it would be a "special" as far as connect IQ. This way the same screen is used for the 23x, 630, and 735 (all really the same family/generation), allowing the same layout for 4 watches, and not a "special" for the 630. (and I'm sure this also goes with the HW and FW too)