Another way to look at potential rim damage in a 5 tire rotation is that any one tire will only spend 1/5th of its time in the spare location, so there is less time to cause damage, and 5x more opportunities to remove dirt and abrasive materials.I supposed the main consideration here is whether doing a 5 tire rotation really makes sense or not. If whichever tire is currently the spare is going to get damaged, then it probably makes sense to just stick with a 4 tire rotation, keep the "regular" spare wheel, and only use the spare if a flat occurs. I certainly don't want to damage 5 BBS wheels over time as they get rotated to the spare location. I've seen plenty of discussion of doing 5 tire rotations here on mud, but I think this is the first time I've seen any mention of the spare wheel getting damaged by the bumpers. That's one of the nice things about having the spare stored inside the vehicle, on the rear door (like on a Wrangler or G-wagon), or on a swing away bumper mount.
Also, fwiw, as a single data point, my 60k spare rim looked like new when I removed it to put a different tire/rim on the 200. The tire had some indentations, but the rim condition was pristine.