I’m surprised it has a transfer case drop, I have OME 2” springs with a Savvy bellyup skid and still run the stock rear driveshaft on my 06 LJ Rubicon with zero vibes.
It might not have had vibes, from the lack of bumpstops I’d say it’s fair to say the lift installer didn’t really know what they were doing so I’m guessing they just threw it on because it came with the kit.
That being said I don’t want to take it off and go down that path I’d much rather just get the CAs and make sure my drive shaft angle is perfect and will before I really wheel it.