Here is an example:
I have a guitar Im overdubbing. I have 2 mics on the amp, one room mic and a DI. All phase locked in a group, and in a track stack.
The artist records and says "hey thats good, lets do the harmony". I click the track stack Aux channel, Command D to duplicate.. and then I have to go in to the mixer, select the new tracks, select a new group, go to the upper left side and phase lock the new group.. its just a long process.
Besides a few rare occasions I have trouble seeing why you would want a duplicate track stack with the same Group.
Just trying to speed things up.