Exactly, a tick/tock product cycle. Apple does the flip of this - using the same case for two models, with different internals. Though they start with the high-end model. Are there as many examples of working your way upmarket?

I think it may also be due to costs. The color e-paper screen obviously costs more, and perhaps a full Steel model would teeter within range of the fashion smart watches (including Apple Watch Sport), where the comparison would be less flattering.