So, with your 22, did you pull the fuse out while the car was running? because That has been known to set the light off. as for the way The system is designed, from what I am aware of, based off of being told this from a very trusted Kia tech (one of the few good ones out there) the drivetrain doesn't seem to care if the front differential is engaged or not. if the fuse is pulled, the clutches in the front differential that would normally engage with the drivetrain just don't activate, meaning the car is just sending power to the rear wheels. The logic in the TCU also seems to not care at all either, which is why you can find examples of AWD cars (A perfect example would be
@AWDGT2 ) being able to do burnouts at drag strips without destroying their drivetrain.
Personally, I have pulled the fuse out of my 18 many times to put it in RWD and have yet to have any issues.