If you have switches A and B in a 3-way setup, you bind A -> B and B -> A and they mirror each other. Or you can create a group and bi-directionally bind the switches to that group and they all mirror each other.
In the group configuration, if any individual Blue in that group receives a command or is manipulated physically, that device apparently sends a corresponding group command which causes all the others to stay in sync. Same result, different approach. Obviously in a 4-way or higher setup, the number of individual bindings quickly gets out of hand, so the group approach might be preferable.
Here's the scenario that doesn't work at present. Let's say you have a number of switches that you want to control using a single group command. For example, I want to turn a lot of switches on at sunset, but other than that the switches are unrelated to each other, I just want to minimize zigbee traffic.
In HE, you can create a group and add those switches as members of the group. The Groups and Scenes app apparently calls into the driver for each device in the group, commanding it to add (or remove) itself to/from the group. It is NOT telling the device to bidirectionally bind to the group or initiate group messages, just respond to them. Group -> switch ONLY, NOT switch -> group.
But the driver, in response to the (presumed) "add/remove yourself as a group member" call is bi-directionally binding the device to the group. This causes all the switches in the group to control every other switch in the group. This is definitely unwanted behavior, and what I and others are complaining about 
I don't have any non-Blue zigbee switches to test, but I would bet that they (or their driver) don't behave that way.
Possibly related but seems like a bug nevertheless: parameter 51. Device Bind Number always shows zero despite the label "counts one group as two devices."
