iPhone 16Pro camera: cropping and aspect ratio?

Contemplating shooting with the 1x "Fusion 24mm" lens in landscape orientation, in RawMax mode.

It seems like the only way to get 48MP is to shoot 4:3.

Shooting 16:9 gets 36MP, which is consistent with a 4:3 native sensor and cropping off 33% of top and bottom bars: 16:9 is 5.33:3; (5.33-4)/4 is 33%.

However, the viewfinder shows a wider image, with faded out wider "wings" that fill the phone screen. This implies that one of the following must be true:

a. It's using the 0.5 "Ultrawide 12mm" lens for viewfinding, although it's capturing the 1x sensor image;

b. It's viewing the 1x "Fusion 24mm" lens and fusing the wider wings on the side from the 0.5 "Ultrawide 12mm" lens; or

c. The 1x sensor is actually 16:9, and it's being cropped for 4:3 -- which would require it to have a lot more than 48Mpixels, and when capturing 16:9, it's arbitrarily discarding half the available pixels, which makes no sense.

A little experiment with occluding the 1x lens (nearest the power button) with a finger shows that (b) is true.

Interestingly, if you push the camera towards a close object such that the wide and 1x lenses start to have significant parallax error, the extension wings fade out, and fade back in only when the parallax is no longer perceptible.

So now I've solved my original question; the only question that remains is "why" go to all that work to show a wider picture, that won't be captured? I personally find it a bit confusing, and have a few pictures where I've accidentally cropped the subject out of the 4:3 frame thinking that the greyed out wings were part of the picture. If I had the option, I would turn it off!