iPhone sales hasn't particularly suffered from being more "locked down" than Android. Why would the watch be any different?
Perhaps because, as everyone, even Apple says.
A watch is not just a tool, a device, like a phone. It's a far more personal device that's bordering on fashion, and says a lot about you, and you choose a watch mostly on how it looks.
Android phones, right now, far more closely mirrors watches than say an iPhone does.
You go watch shopping, and you find all shapes, sizes, designs, styles, process and brands of watches out there, but they all have the common theme of telling the time, perhaps in slightly different ways.
You see how this mirrors Android phones.
Shapes, Styles, Prices, Brands, but all have the common theme of Android, albeit in a slightly customised way.
That's a very good Android Analogy to watches now.
Apple's controlled 2 models of a phone or 1 model of a watch in 3 colours with a few strap options, in no way at all mirrors with world of watches.
I think you can see what I mean here.
If we end up having one Apple watch, quite controlled, vs perhaps 20+ Brands of Android wear watches, each perhaps with 2 or more designs, that will be a strong force when it comes to allowing customers to pick designs, and styles as they do now when shopping for something they are going to wear, and as I say is as much about looks/fashion as about it's function.