This probably depends on what you mean by "smart"

In the old days, dumb phones were defined as devices that shipped with a set of features with users generally being unable to add new features themselves

And smart phones could be extended by users because they allow installation of apps, etc

But I don't think this applies to smart watches: it seems like the difference here is that a smart watch goes beyond "dumb" by having phone/internet connectivity to display more than just times and dates