Different swipe gestures to dismiss iOS notifications in locked vs. unlocked phone-- why?

Question

In iOS 10, on the lock screen (or in the notification center), swiping up on a notification does nothing and to dismiss a notification you have to swipe left and tap "Clear".

On the other hand, when the phone is unlocked and you get a notification, swiping left does nothing and you have to swipe up to dismiss it.

I understand why swiping up isn't a valid gesture for the lock screen, because it would conflict with vertical scrolling when there are multiple notifications.

But I'm baffled why "swipe left" wasn't used as a universal gesture to clear a notification. Apple is usually good about design consistency, so I assume I must be missing some advantage of this design.

Is there a usability advantage to the current implementation where the most common operation with notifications (dismissing them!) requires a different swipe direction depending on whether the phone is locked or unlocked? If so, what is the advantage?

Answer 1

Scrolling pattern of that instant.

The percent of up/down scrolling is too high than left/right when you are on a unlocked screen. On unlocked screen a user is generally using some app/website meaning he/she is scrolling content up/down constantly, so the current finger flow is up/down. It could be an effort of not breaking gesture flow of that moment.

When you are on unlocked screen you mostly use the left/right gesture to unlock your phone. That's the mental model you have developed and I think Apple didn't wanted to break it.

I couldn't find any solid resource to support this, but this is my own opinion.