well, in DoW2 you operate from Strike Cruiser Armageddon which is the same model of ship as the one depicted, then at the end of the game a space battle goes down and the battle barge Litany of Fury comes along and the size comparison is like comparing a cat to an elephant
Just watched it. I really don't know where Relic got their reference from, or how GW could endorse it as being canon.
The ship in my pic is based on the miniature which was released the best part of a decade before DoW2 came along. Most, if not all, of GW's artwork also references the design of the Battlefleet Gothic miniature.