I'd add to that last comment, it appears we engage defensive rucks only wide where the loosies are on it with speed. Rucks through the guts would seem to have us standing off. An indicator of physicality needed or a coached/planned response?
It's about only contesting breakdowns where you either have a strong chance of stealing the ball or substantially slowing it down without committing too many players. Most of those opportunities will come further out wide where it's easier to get the ball runner isolated.
It's definitely a coaching direction and has become the norm for most teams in the modern game.
Finding the right balance is the crucial part. If you contest too little you give the opposition quick ball too often and if you contest too much you leave too many holes in your defensive line.