I'll give you my $.02 on that Gordie...
There is a relatively new offensive system called '3 high' where, at 5on5, a forward rotates out between the D, creating all sorts of attack options while also allowing for easy retrievals and keep ins. This came into the league 5 years ago and about half of the teams use it now to some degree.
At first a lot of coaches didn't love it because it pulls a forward away from the net, (and after all that's where the goals are scored) but what coaches have learned is that it wreaks havoc on defensive structures.
For example, a typical box and 1, like what the Bruins have deployed for 20 years to great success, does not allow the center to venture above the tops of the circles, his job is to stay low, support the D and be a second layer if a player gets beat. Well, when the other team puts 3 guys out above the circle and your system only allows 2 guys to go out that high, the other team has an advantage. They can run plays and give/go's that create problems. Teams that run this system (like Florida) give the Bruins fits, because if the Bruins chase, they're out of their structure, and if they stay home it looks like a power play and leads to long stretches of zone time.
This season, the Bruins tried going to more of a man to man with Monty, which really flopped. Then they went back to Julien's box+1 which helped, especially against teams that don't roll out 3 high, but they still struggled against teams that do.
I think, what we're seeing now under Sacco is something in between. They play a box+1 but the center has more freedom to play out high when the other team sets up that way. It's not quite a hybrid (where the forwards play man to man and the D play zone) and it's not quite a box+1 because you can have all three forwards in a line across the tops of the circles. But there is still some kind of a disconnect with regard to what they're doing because the other team starts roaming (like NJ did), our guys seem to get lost in coverage.
Long story short, I think the box+1 is going the way of the dinosaurs because offensive schemes have evolved. What's more, I'm not sure the Bruins know how to adapt.