As long as we don't go back to the Ross Lyon style of the naughties, that was truly terrible, all the top teams move the ball fast and score heavily as it is.
I'm not sure 666 will make a lot of difference, it may even hamper the weaker teams more, seeing more blowouts, which isn't a good thing.
Although almost completely ineffectual to a Lyon defence style of game plan the intent of 6-6-6 is to counteract the congestion not necessarily contest.
I completely agree that this rule will have insignificant impact, all it does is even up the contest at the centre bounce which in reality will favour ball winning mids in an attempt to reduce congestion and speedy outside mids on the spread. i:e freer flowing footy.
So yeah high quality mid teams will probably benefit and bury some teams but the "optics" will look better