When "Enable process merge for normal users" is OFF, still there is a choice to Merge

In Admin > Configure > Viewing Options, although the “Enable process merge for normal users" is OFF, users (in both Minimode & user) are still able to select the icon on lower right to expand the process into the current map. 

Is there a reason why turning this to OFF seems to have no effect? And, if we wanted to turn this merge feature off, is there another way to do it?

Thank you in advance for your inputs!