I am fairly new to cocktail making, but the end result here looks so drastic. The guy on the left was clearly shaking much harder, but it seems to have resulted in a better espresso martini (more foamy, at least). I'm a bit worried that when I shake too hard, it will over-dillute the drink? Can someone help explain what's going on here?

https://www.youtube.com/watch?v=lhBkuRKQk2s&list=PLhHPknzkhSz5nWYKgEUm-5YGT9-NXapgh&index=1