The Sloan report didn't indicate a demonstrator car (shown in the very last category on the wholesale order sheet) for whatever that is worth. It also says the car was financed through a bank or other alternate source instead of GMAC or cash....so perhaps it was just a customer order. I mean, how many convertibles were likely ordered in the ordinary course with an engine block heater? The car still had the block heater plug under the hood when I bought it! I was incredulous that it could be original until I saw the order sheet.
The option sheet confirms you could have your LeSabre Custom just about any way you want, although I don't see a cornering lights option. That looks like a Centurion specific item. The 1972 Buick catalog shows LeSabre customs in hardtop and convertible forms pretty well equipped with rally wheels and the customline boot cover so maybe it wasn't that odd for a LeSabre custom. While I've never seen one quite like this, I haven't seen very many of these at all with the low production numbers (about 2,037 LeSabre convertibles and 2,396 Centurion convertibles). Lord knows how many have survived in the wild.
I was hopeful someone might materialize with some connection to the car or the dealership in Iowa during the BaT auction, but disappointingly that hasn't happened.