A change to avoid a shudder sounds very plausible to me. Didn't Mitsubishi drop the LSD in 1991 (in the USA)? They likely realized that in the US the LSD was not a big selling point and the shudder might have caused customer complaints.

My repair manual has a revised page added to it. It updates the procedure for measuring the V6's differential carrier. Originally the manual incorrectly indicated that the V6 LSD was the same as the 4 cylinder. The revised page doesn't show a different arrangement of spring plates and disks though.

89 Raider V6, manual, 5.29 gears, ARB front locker