The cause of this is image-stacking.

The phone takes ~20 frames, over 0.2 seconds. In that time, lots of people and things in the frame move.

Optical flow is used to track all moving parts of the image, and then 'undo' any movement, aligning all parts of the image.

Then the frames are combined, usually by, for each pixel, taking something like the median or throwing out outliers and using the average.

When the optical flow fails to track an object in more than half the frames, the 'outliers' that are thrown out can in fact be the image content you wanted.

It happens with leaves a lot because they can flutter fast from one frame to the next, so tracking each individual leaf is hard. A few bad tracking results on more than half the frames, and all you end up seeing is leaves where there should be a face..