It seems that he means that the single rotation in the webbing before sewing it back on itself keeps it from laying completely flat. I guess some people like that.
I also got an email from StrapMan today. I had contacted him earlier in the week about the possibility of getting a strap-set made from the seatbelt webbing (and my email probably is why they added the new sling type). In the email he told me that they've already sold about a hundred of them. Either the lurker audience here is larger than I realized, or there is another purpose for this sling that I don't know about.