Hey- Brian from Vitrima (the guy in the video). I think you're right, Vitrima Lens isn't for advanced stereoscopic film makers.
But most of the skydivers, snowboarders, etc. who we talked to don't really want to be advanced stereoscopic film makers- they just want to film in 3D. So Vitrima is a great way for them to record in 3D just by putting their GoPro Camera in a case.
Hey Carlo- It's Brian (the guy in the Vitrima video). The GoPro can record in narrow field of view, which doesn't have any fish eyed effect.
But you are correct that if you were to do it improperly and use the GoPro in the fish eyed mode then it would look awful.