Not to be adversarial, but the flat tire is there because there is an ambient light sensor visible in there. If the flat tire (and light sensor), were hidden behind the bezel, then it wouldn't function and so there would be no need for it. No, the other watch simply doesn't have the ambient light sensor and so there's no need for the display to be cut short, which creates the flat tire.
See below and note the small red dot in the center of the flat tire.
Yes, the connector is there but I don't believe that it's a reason for the flat tire. They could connect the same way along that edge, even if the screen were fully round.From what I understand the flat tire is also the location of the ribbon connection that drives the display's pixels. That's why the bezel is so thin all around. The other manufacturers have a thick boarder all the way around their screens. These boarders are hidden under the thicker bezel. So even without the ambient light sensor they'd have to have an area to connect the actual screen to the processor. I like the thin bezel on the 360 but I think I'll hold out until the flat is gone.