I haven't seem real comparison tests either, so I decided not to push for a big mod before the roadtrip (a dead transfer case 600 miles from home is not fun).
Yeah, "modern" Jeeps don't have lockout hubs, so the entire front drivetrain will spin. Perhaps the people who reported MPG improvements had a messed up transfer case, ie partially locked up gerotor coupling, causing a bit of bind going down the road?
The KJ transfer case will help the plan to lift the entire drivetrain and build a slim transmission cross-member, to help clearance off-road (since I actually use it off-road). The transmission cross-member hangs down a lot, so a slim one might help aero too.
