A smartwatch in a 45mm case is now pretty easy to build. it won’t be fancy, but an esp32 plus screen in a 3d printed case is something I could make.

A basic mechanical watch movement is something I can’t make. (I have made a case and dial out of aluminium/brass though.)

But, the point I was trying to make is that adding a complication to a smart watch is trivial, something that can be done in a few hours and shipped to everywhere. Adding a complication to a mechanical movement is a lot harder, especially as the iteration time is long.

It’s harder to build one smartwatch from scratch - it took decades and trillions of dollars. However, having already built N of the same smartwatch model, it is much easier to build the N+1st than to build a mechanical watch.