It's MAGIC!
This is from MAX 's help files

Copy method: Creates a completely separate clone from the original. Modifying one has no effect on the other.

Instance method: Creates a completely interchangeable clone of the original. Modifying an instanced object is the same as modifying the original.

Reference method: Creates a clone dependent on the original up to the point when the object is cloned. Changing parameters for modifiers that were applied to the object before the object was referenced, will change both objects. However, a new modifier can be applied to one of the reference objects, and it will affect only the object to which it is applied.

I mentioned before that there are things are love in MAX and things I hate... This is absolutely a nice thing to have.
Another thing is that the copy command is in some way an array command too. For example, you make a box want to copy it 1 meter to the right. Before the command finishes, you see a dialog where you choose the method (copy,instance,reference) and a number of copies spinbox. If you set it to 5 for example you get 5+1=6 boxes each 1 meter from the other. Nice isn't it?

Max has many commands and methods because it has many capabilities. I am just trying to choose some of them that are easy to add to MoI not because they are Max's features but because I've found them useful. I would never add a wishlist item for animation because it is too early but I would like to see more flexibility like the one I just described.