Why YSK: I’ve been seeing an increasing number of phone photos shared online in 9:16, 9:21 or similarly tall aspect ratios, often with parts of the subject cut off. I’ve asked a few people why they cropped their images that way, and none of them knew they were cropped.
You can check it yourself, just set ratio to 3:4, aim camera so some object will be in corner, and then change to 9:16/full, or whatever that’s bigger. You will see that the object won’t be visible. And sorry if I made a language mistake.