Re: Tail fin
It is undeniable that *some* 787's are assembled with pre-painted tails, and others are not. Google "Everett 787 line" images and it's obvious... but it's also obvious that this video is fairly generic: much of the same footage has been used for other customers ("Scoot", as noted above)... but the videos become specific once the aircraft gets to the paintshop. And there's your real clue: if the aircraft shown been painted in BA colors hadn't actually had a pre-painted tail, why did they mask the tail in the paint bay?
So the bottom line is that this video is a hodgepodge of stock footage, (possibly) CGI-modded stock footage, and actual footage of the aircraft under discussion!