If you have the oem rock guards. Couldn't you install these on the rear of the rock guard? Just a lazy thought. But for the op argument when your rear tire hits the mud or muddy pot holes with momentum it will push the mud or muddy water forward. Doesn't have anything to do with tire tread.
I get that argument if I just had it done. 12 years sitting in the driveway ive had to replace 2 sets of headlights due to clouding/yellowing from the sun. My white linex is still white. I think 12 years is enough testament.