I think the RE agent grabbed some cheap wide angle lens or saw two with two significantly different prices and went the cheaper route. You can get a good 12mm full frame rectilinear wide angle.. but it does cost. An 8mm lens will be a fish-eye, and you can get them at almost half the price of a rectilinear(or even less). My 12-24 cost around $1k, and I shopped to get it at that price.
I suspect the cheap lens route. The vignetting at the edges is uneven and soft on one side. It may be a ‘wide angle adapter’ for a cell phone or point and shoot.
