as far as vampire lords go mechanically, i think it's kind of dumb to assume the one in the game jam video is the one we'll be getting in the DLC. that was something somebody threw together in a week for fun and it was obviously unfinished. whatever's in the DLC will look and feel considerably more polished.
as far as lore:
Regarding [pretty much everything in lore that hasn't been seen in a game yet], keep this in mind: Most of the books and legends concerning [pretty much everything] in Tamriel are based on folklore and half-truths.
adjusted this a bit for you but - this. there's exceptions, obviously, like multiple corroborating stories about a thing, but pretty much everything is [censored] grandiose speculation until we as players witness it with our own eyes, especially for something as mythical as vampires and werebeasts.
using "oh it's against lore" as an argument against something doesn't really work nearly as much as people want it to.