When I was boxing I always kept my left shoulder up and my chin tucked in. When I put out my left hand it caused my shoulder to rise further making it almost impossible to be hit by a right hand, certainly not on the jaw, maybe the top of the head. And my left side was well advanced. I also moved to the right, alternating by occasionally standing still to invite a right hand and slipping it to my left, leaving the opponent off balance and open for a left hook and a right to the body. Won quite a few fights that way.
Boxers don't use this style any more, instead, keeping their hands low and their faces uncovered. That's asking for damage, and they get it. I had 62 fights and never even had a nose bleed. was knocked down once by a flash left hook on the ear, no count, jusr rolled over and up, before I even knew I'd been down. I remember hearing bells ringing. Odd feeling.
Mayweather throws that right very accurately, with not much power because it's more or less a direct punch, and aimed like a dart, making it very accurate.