Great vid, enjoyed it. Regarding the line-out: I think it’s indeed more a speciality rather than a size thing. Certain players are just really good at it (Cameron Woki and Florian Verhaeghe ‘spring’ to mind).
But I noticed that today a lot more teams just await the maul and rather set up defence instead of compete. Which makes it all the more interesting when a team does go all in to target the opposition line-out. I remember New-Zealand doing it to Engeland before the WC once. So you’re probably right.
Edit; does feel like the game is evolving to a sort of sevens style of players, who are more interchangeable. Most modern hookers just have the build of a center / flanker and a lot of props are way leaner than years ago (or this is just a gut feeling)