No really, you must have missed a lot of things to be done both Ego Draconis and Flames of Vengeance in 45 hours. I know where everything is (part of that was form beating Ego Draconis 3 times before DKS came out), so I didn't need to wander around looking aimlessly, and it takes me about 60 hours per playthrough.
Well unfortunately I have no idea how to prove it to you beyond the fact that I'm only missing maybe five secret achievements. Ask me and let's see if I've done it or not?
My next playthrough would likely be much shorter as well because I'd be skipping through most of the dialogue having read and heard it before.
The thing is that however you cut it, there's much less than 100+ hours of content I see marketed everywhere.