I disagree with that; in my mind the distinction is not whether the manufacturer wants me to to run arbitrary code, but whether they expect/intend themselves to be able to run arbitrary code after the device is shipped. So ex. a dumb digital watch that just has time/date/alarm/stopwatch functions is fine because once it's sold the manufacturer never expects to update its code (and said code is probably on actual read-only ROM), but an Apple Watch is intended to run arbitrary code - just that Apple locks down that ability to code that they allow, which I do object to even though Apple never intended to let users run their own code at will.

Most of them are a little more than minimal, almost all of the ones I've seen are running full buildroot Linux with tons of shell scripts gluing stuff together and the main app in C++.