More or less.
In the sense that on the one hand a team keeps the ball phase after phase - and on the other hand another team kicks a lot of their possession away to get good field position and feed off mistakes - yeah, they are the extremes as far as use of possession is concerned.
It is not as simple as that we know: the Brumbies did a lot more than recycle the ball, and we know that the Bulls and Boks do more than just hoist and chase and pounce. They were/are just team signatures, but they are signatures written on a tapestry created by laws and the interpretation of them, plus the conventions that referees use (those top referees are doing this and that so we will do this and that, even allow the ball to be put into the scrum skew.)
Brumby Ball was marginalised by opponents finding ways to kill the ball - tackling and sliding down the opponents side of the tackle, tackling and not releasing yet standing up and fishing for the ball all in one motion, never releasing - (and we had to listen to commentators say "what a great player"). The laws to stop that were there but the referees wanted the game to flow and they let it go more and more each year until we have what we have today.
It was also marginalised by a law variation allowing the tackler to stay on the opponents side of the tackle. That was a killer of Brumby Ball. I was never a great fan of Brumby Ball but now we are at the other extreme, whereby retention is too risky and the ping pong prevails.
If this new tactic of the SANZAR refs - to enforce the law whereby tacklers have to let go of the ball and the tackled player as the first item in the tackle transaction, perhaps teams will not be as concerned as they are now about losing the ball on contact.
Maybe then the ping pong will stop; maybe then teams will find that there is a dividend from holding onto and using the ball and not hoisting it for the other team to stuff up.
Yes it is another variable - but it should never have become one: the law requiring hands away first was there all the time, and only sad Don Quixote characters like yours truly questioned the convention of ignoring it. They saw the escalation and tilted at the windmill and nobody noticed.
We should beware of laws and their precursors, ELVs, because they have unexpected consequences. But hardly anybody mentions the consequences of referees ignoring the laws, or of interpreting them in a way they feel is better for the game.
After watching rugby for more decades than I care to remember I reckon that such referees hardly ever improved the game at all.