Rick,
I'm sure they don't own all the bikes they sell seats for. The margins and sales volumes are not large enough. They borrow them from somewhere, or get people to send them measurements. I am now a veteran of this process, getting the first Knight Designs footpegs for the NT, and the Mick-o-pegs for the NT, and last week I took the Super10 to Powerlet so they could design for it. And how easy is it to find an NT? No one here has posted saying they measured their bike for Corbin, have they?
Anyway, judging from the results we see here, I am wondering if they tried to make the NT seat without getting their hands on one, based on measurements taken by some owner somewhere, who didn't do it well? Measuring irregularly shaped objects is hard.
I have only owned one Corbin seat ever. I acquired it used as part of the package when I bought my VFR. It was a nice looking seat and comfortable, and didn't have problems like this NT seat has. But I switched back to stock because of fitment issue - the Corbin didn't latch properly and would shift around while I was riding, and I didn't find the stock seat uncomfortable so I just switched back.