I was about to disagree with you, then I remembered the little red dot they put on the crown of the Apple Watch 3 to differentiate it from older versions. That was purely about demonstrating the owner has the newest iteration.

No surprise there.

I was more referring to the fact that colors are available only in certain years. So if you have the "Rose Gold" iPhone, this identifies you as being on the latest release in one year. And also identifies you as being a year out of date when they don't make that color available in the following year.

The red dot differentiated it from the non-cellular version.

In case we forget what we bought and accidentally try to make a call off our version of the watch for commoners.

You can make a call from your non-cellular watch, provided you're in range of your iPhone.

Parent is slightly off in the details but the basic point is correct: the dot went from a filled circle in one generation to an open circle in the next. There's no functional reason for this, and the form of the crown itself didn't change enough for there to be any real reason other than for "spectators" to be able to distinguish the models visibly.

(And I'm not casting a stone here: I say this as someone who bought a Watch from each generation.)