Genuine question: Did you include "rectangular" because you would prefer a circular smartwatch? I genuinely don't understand why people would want a round smartwatch. I don't see how a round screen would provide a good UX (this is why they don't make round monitors, or round smartphones).
Even if watches are traditionally round, I wouldn't want to have to build a UI around the constraints of a circular screen.
Whether you implied this, I have seen multiple people voice their preference for a circular smartwatch, so just trying to understand the logic vs. the constraints it would impose.