This Dark Souls 2 Lore video primarily covers the Origin and happenings of Queen Nashandra of Drangleic and her interactions with King Vendrick and the Cursed Undead.
The Legends of Drangleic Dark Souls Lore video series tends to attempt to enter the psyche of the character the video is focusing on; imagining the Lore of Drangleic from their perspective. So if some of the lore seems inaccurate it may be due to the fact that it IS false because the subject of the video (Nashandra in this case) is misinformed or does not know the whole truth.