would be hard to test on the Jeep but if you look at airplane engines that have dual plugs and dual ignition systems turning one of them off would result in an rpm drop - it's understandable with magnetos since the spark is weaker on them compared to an electronic ignition, but the same thing happens on the airplane engines with electronic ignition and magneto (for the second set of plugs), turning the magneto off would result in an rpm drop, lot less than if you turn the electronic ignition off but there is still a difference - can't remember the exact numbers but i think was something like 250 rpm drop when only one magneto was on, in the mixed setup something like 50 to 100 rpm when only the electronic ignition was on - not as dramatic but looks like there is something to gain.
Now, there are some differences in the chamber on these engines and the plugs are at opposite sides in the chamber so i'm not sure how much of that would apply on the jeep 2.5, probably less obvious but there is something that could be gained. I wonder if a plug with multiple prongs would result in better gains.