If i got and created three (1,2,3) groups of rules under "Responsive & Mobile Design".
I edit my page and set some layout sections to only show for rule set 1 and 2 but not 3.
Later i remove those rule sets and decide on 2 new ones (4,5).
When i go to edit a layout section
1. The old class rules are still in the field
2. AND had I in fact named them the same thing (1 and 2) these classes would also have a conflicting effect front end.
This create all sorts of display problems.
Either on removal of a rule set also remove the classes or "under the hood" the naming convention cannot be stored identically so group "One" that was created twice would have to be "One" and "One_1"