Since the app seems to seamlessly adjust the picture so it doesn't rotate when you change the actual smartphone's physical orientation, what's the point of rotating the phone mid-shot?
Take the example of the two women sitting for coffee... why does the camera-person bother rotating the phone to horizontal in the middle of the shot? Why not just stay in place?
I can't think of any time when that isn't what I want.
Area of vision man. It is not wasted space to see a horizontal plane, as that is what we expect to see when looking at anything. Vertical video simulates the effect of straining to see through a partly closed door it is tangibly horrible.
Horizontal video simulates the effect of straining to see through a partly closed Venetian blinds it is tangibly horrible.
Now, is this any more correct? Or is it an equally arbitrary personal opinion?
The move to "wide" screen was also the move to short screen. I don't find anything natural about it; I expect to be able to move my eyes up and down as well as left and right.
A preference for short and wide screens seems more cultural than natural. Even granting that humans have better peripheral visions along the sides than top and bottom the current screens fall short in capturing this range.
My beef with most vertical videos is that people typically do not make good use of the format; there's nothing intrinsically bad or wrong about it.
In another comment you said that 4:3 is a reasonable approximation of normal human visual field. 19:9 screens don't map to this; this restricted height works well for consuming certain current entertainment offerings but I don't see that a preference for it is objective.
If area of vision were guiding screen design we would likely see more of what the current Surface 3 offers.
Vertical-format video has the opposite effect: you might call it anti-immersive. It boxes the subject up in an intrusive frame and makes you feel like you're looking through a hallway or some other obstruction.
Though, i think i'd prefer this style app if it just picked portrait or landscape, and adjusted between just those two states dynamically. That would be nice if you accidentally shoot in one, and decided you wanted the other. Which happens quite frequently for me.