While I agree with your point, my take is that the average UTV owner can not fabricate or even procure a KOH specific roof. And sportsman is in theory for the average UTV owner. Should everyone use a roof of some sort? Absolutely.
I've had a few calls about this issue, and people ask me why I said that an 1/8" roof isn't required for Sportsman. First, because when I spoke with Dave, that is how it was explained to me, and second, last year, a few people passed tech for Sportsman with roofs that didn't meet the main U4 rules. Here is an example :
That is the plastic Kawasaki accessory roof, and it was used in sportsman last year.
I would suggest that anyone who has a tech concern contact Dave directly. I do not work for U4; I merely post my interpretation of the rules to try to simplify for those who might want to race.