Resolution: Investigate
Category: Tools

See attached .blend. Try selecting one object from both groups and then invoke shift-g -> objects in same group. Note how objects only from the group of the "active" object are selected. Another interesting thing to note is that the behavior is the same for shift-g -> children. You can see this by selecting the parents of the cones and invoking the command.

These cases should work so that they do the selection for all selected objects instead of just "active" one. The old way of selecting still works in this case but only if one object is selected.