Not allowed? Don't have a choice? Neither of the articles you linked to suggest such a thing. It sounds like she had just gotten the watch and was still learning how it worked. And yes, it seems she's learned that getting notifications while in sight of tv cameras isn't a good thing, and figured out how to keep that from happening. I admit I'm not privy to how Pelosi feels about wearing a black square on her wrist. Maybe like me, she thinks it looks classy. Maybe she hates the look, but finds the Watch useful enough to wear it despite the not-optimal look. But whichever it is, she definitely has a choice whether to wear the watch.
I'm just pointing out that you not liking the look of a dark rectangle on people's wrists is just your preference/aesthetic/opinion. I, for one, think the dark rectangle looks fine and classy. I understand not everyone feels that way. But I hope you can see that some people might actually choose to wear their watch with the screen off, and prefer that look, even when they have the choice of using AOD.