Without a full size spare if you get a sidewall puncture and you are on a rocky 2-track road, you might not have the clearance to get back out again without the height of a full size spare. In my 2003 Pilot I could replace the original smaller tire spare with a full size tire in the same place under the car. Also no need to unload the car to drop down the spare. As someone who has gotten a sidewall puncture, this is a real concern and lessening the risk with better AT tires with stronger sidewalls doesn't appear to be a current option with the 20" tire size.
