One thing I noticed in the video you included: when the shot is following him from behind I noticed that Van Hazel's head is completely stationary, no lateral or up-down movement. Amazing!
Thats been a big thing for me to learn - if you want to be able to breath without taking long pauses, your whole torso needs to move, and it creates a very natural motion to pop your head left or right to breathe a pocket of air
Another bonus to rolling -- it is initiated with your core, so it uses large powerful muscles. Once the roll is initiated you can feed your kick and your pull with that momentum. You end up using more powerful muscles to feed your stroke, so you can pull harder without wearing out your arms.
A few years ago, I did a swim workshop taught by Dan Bullock from Swim for Tri (https://www.swimfortri.co.uk). His technique is optimized for long distance open-water swimming and emphasizes smooth, energy efficient motion.
Watching him swim with literally no splash on arm entry was amazing. And torso rotation far further than
Most of my previous swimming was for water polo: short, sharp sprints, mostly head-up freestyle, focus on power and claiming space, often jostling with your opponent. Exactly the opposite of Van Hazel and Dan Bullock's focus on perfect technique.