Airing down has been an off road tactic from way back when. Not much to gain with so little sidewall and you increase risk to damaging those fancy rims. Ever try running a hard tire forklift off the pavement?
I've ridden my chromed up Harley (16" wheels) on many miles of dirt & gravel road. I do ride it like a wussy, real slow as to not grit blast all the custom plating. It is also lowered, obviously not built for off pavement. I have come upon fords in the rode. I have only turned around at one. I could see it was rocker panel high to a 4wd that day. But I have crossed many and even on my way to a dyno-tune appointment I crossed a flooded area of road I am very familiar with that always floods. It down poured just as I was about to get on the bike and didn't stop till after I got the shop. I keep my appointments. I know this is an issue for bike (Harley anyway) shops when it rains.
I guess you can drive most anything with most any tire size on most dry dirt road surfaces. But if I was figuring on that being a regular occurrence I would want wheels and tires most appropriate for that use. There are good compromises for combination on/off road use.