Three points to consider regarding discoverability:
- Swipe gestures are invisible. Swipe to go back might be easy enough to understand — although in my opinion, it should always be accompanied with being able to undo that action, i.e. swipe back forward again, and a mechanism to avoid losing data. I’ve had situations where I was typing something, inadvertently swiped back (swope back?), and then on return the text input was gone. In any case, other swipe gestures might not be worth the trade-off between discoverability and reachability. I mean, there was a time when we had a clearly visible scroll bar and navigation buttons, making clear where we were both in the document and in the hierarchy. How much of that can we omit before the user experience suffers?
- Swipe left/right only works when there’s no 360° scrolling. Which means that some apps will always behave differently than others. Not sure this is a good idea.
- How easily are drawers understood? My grandma doesn’t get the Apple Maps interface at all, and frankly I’m often puzzled myself. Google Maps is not perfect either, but is far more obvious to use. It’s not just about the drawers, but I think their swipability could be more apparent visually. I feel they are also fidgety to collapse again, but maybe that’s just me.