It has a black background because it's a VFX test and would be composed on top of the trailer once that was available. They're not going to edit the trailer video in the same composition (or even file I'd guess) as the title. My biggest doubt is that the flame effect is horizontally mirrored. Whether that's because it's a legit early pass/proof or lazy part of a fake, who knows.
It's more damning that whoever caught it didn't take a video of it. Who doesn't have a phone/camera that can record video in this day and age? 'Skysunder PTR Information' tab also seems a bit forced. They'd have no reason to collect together PTR notes online at this sort of stage; much more likely they have internal document(s) used to track changes.