The subtext to this tweet is a criticism of Force Touch in terms of discoverability. On this particular case, I don’t think this is a UI issue. In fact, it’s an ideal use of Force Touch in the Apple Watch interface; revealing an action that relates to the context of the current screen.
Concessions have to be made for a screen canvas that is the size of your wrist. If a button was present on the screen, I have no doubt that Drance would have found the Clear All function sooner. If we were talking about an iPad, where more screen space is available, I’d agree that some form of Clear All action should be more obviously present, probably as a text button at the bottom of the list.
The reality is an Apple Watch display is simply too small to put everything on screen at once. Some things have to be slightly obscured. Secondary actions cannot afford to take up persistent space in many cases: there simply isn’t the real estate. Some concessions have to be made and I believe that the right design decision was made here. If you use ‘Clear All’ frequently such that it feels like a primary action, you are using notifications wrong and should consider turning off alerts for some apps in the Apple Watch settings.
Clear All is less important than actually viewing the list of notifications, adding a button for Clear All would impair that (far more) frequent activity somewhat.
Heck, even on macOS most actions for the current app aren’t visible onscreen all of the time, but we still know they are ‘there’ because we have habitually learnt the vocabulary of the operating system. Things like using right-click, popover panels and menubar items become ingrained behaviours.
Apple is establishing a similar behaviour for Apple Watch; Force Touch to reveal contextual actions for the current screen. The actions should be relevant to the modal view as a whole, not connected to a particular element of where you pressed down.
Force Touch to Clear All is a coherent use of this system function. Becoming familiar with Apple Watch should involve an instinctual feeling to deep press screens when you want to perform a contextual action. This is consistent across Apple’s apps and should become learned behaviour over time.
Even when there aren’t any contextual actions for a view, Apple Watch UI will always respond with a screen bounce animation to suggest that the user was right to attempt the gesture and should try again on another screen.
Maybe watchOS is too new for it to become a natural instinct yet, maybe Apple should help educate users better about it. I don’t think the premise of placing Clear All action behind a Force Touch gesture is a bad design decision, though.