Haven’t watched the video but he is one of the reasons and a strong one. He has really big hands and has been pushing flagship devices since forever.
I have really big hands too, and even with those, really big phone sizes are just not practical, IMHO. Unless one has giant NBA player tennis racket sized hands, past 6” to 6.2”, you just can’t comfortably hold your phone and reach every part of the screen without shifting it around all the time.
I have pretty small hands and I use a 6.7" phone with no trouble. (As a size reference, I can comfortably reach the frets on a 3/4 size electric bass or a guitar, but a full size electric bass is too big for me and I can’t play without moving my hand a lot more than you’re supposed to.)
I don’t disagree you may find it comfortable, I just genuinely don’t understand how you do it. I guess you don’t mind the shuffling around that comes with typing a button in the opposite corner of the screen, but I personally do. When holding my phone with one hand in a position I can type in and the phone just won’t slide down to the floor, my thumb just doesn’t reach the opposite corner of the screen without shifting the phone in my hand.